So you only have enough time for either finishing off the adventure, or dealing with random encounters, but not both. Therefore any solution requires spending very little time.
Simple Narration
One acceptable way to handle it seems to be to narrate it away. It's entirely legitimate to narrate their travel through the wilderness and cut to the chase, so to speak. Your players won't object, and are even likely to be thankful that you responsibly paced the session so that it had a natural and enjoyable end.
I wouldn't bother with any resolution mechanic, even a simplified one. Sometimes travel in the wilderness is uneventful. Take advantage of that, plus your power as the controller of the world and your responsibility to pace the game well, to just make this time one of those uneventful travels.
If you feel that it is really unrealistic for this trip to be uneventful, mention what trouble they encounter along the way in the past tense, off-handedly, and conveying that "of course" they handled it without any difficulty. For example, encountering and quickly dispatching an already-weakened patrol of orcs can be glossed over in a sentence, giving them your acknowledgement that the PCs are kick-ass and that was nothing to deal with. Lead right into a description that places them about to engage in the final action of the session and you're good. In systems where encounters lead to XP of some kind, I wouldn't hesitate to give them a token amount – unless the resistance was really beneath them.
Alternatively…
Roll For Complications
You don't want to take any time dealing with the travel, but that doesn't mean it has to be meaningless. Taking a page out of Dungeon World, you can call for a roll to test something during the "perilous journey". Decide on a possible complication of the journey that might lead to a mild consequence for them to deal with at their destination.
Perhaps you have them check if they move stealthily, and when they arrive the inhabitants have been warned of the approach of armed people, or not. Perhaps they make a survival check to determine whether they arrive hungry. Perhaps their pack animals were spooked at some point, and an animal handling roll will determine whether they're down one donkey and low on torches and lamp oil as a result.
Whatever complication you think will be interesting, present the potential event, describe the possible consequence, and call for a single test of their abilities to do well. If you like, you can come up with two or three (quickly), and give the players a choice about which one they want to risk on a die roll (they get success on the others free). This is a very quick and flavourful way of making the travel meaningful while concentrating their attention on the important thing: the final action of the adventure.
Other answers (including my own comment above) address possible reasons your players are doing this, and possible solutions to mitigate it. But you're not asking for value judgements or how to stop their behavior, so here's my best shot at a neutral analysis of how a D&D type setting could respond to the behavior.
These are some responses I've used, or considered using. They aren't intended to be used all at once, and some are much harsher than others. Players engaging in this kind of action are calling attention to themselves, and the world will respond accordingly, but as Flamma points out punishing players is a bad idea. These are possible reactions, intended to make players more aware of the consequences of their actions, create complications, or give the world a bit more depth. Consider these springboards for your own ideas, and always consider what you're teaching the players about your game and your world before you do something drastic or mean.
First, a little context
Depending on the setting this behavior isn't quite as shocking as you're making it out; a gold coin in most D&D editions is worth 10 silver, not 100. Still, the denomination is unusual and even if a place of business makes hundreds of gold a day they're unlikely to see a lot of gold coins go through the till.
"I can't take that; nobody here can make change for it."
Sure, the party isn't expecting the local innkeep to make change for a platinum piece... but nobody else can either. It's like trying to pay someone with a barrel of crude oil; sure it's worth a lot, but what is Bob the Fishmonger going to do with it?
Same applies to objets d'art, handfuls of gems, and rare/ancient/foreign coins. Finding someone who can evaluate and buy their stuff could be a fun RP adventure, and there are all kinds of stories you can tell around an auction house.
Lavish them with inconvenient praise
Your players are clearly disgustingly rich philanthropists with no sense of proportion. Swamp them with beggars, inundate them with charity representatives, give them tedious award ceremonies to attend in their own honor. If they can't maintain the level of charity to which the locals become accustomed, turn the crowds against them, for reasons the next point makes clear.
This is largely going to be local color, but if the party wants to engage then it give them some toothy moral dilemmas.
The economy booms and crashes
First everyone runs out to spend their newfound wealth. It spreads around, people get excited, luxury items become popular, new businesses open, people move into the suddenly prosperous town... but it's all supported by itinerant charity.
Soon after the party stops their lavish spending or move away, the town can no longer afford its new luxurious tastes. Businesses close, investments are lost, unemployment rises. With an increased population the town can't return to its old status quo: no longer able to afford imported food and having grown faster than its farms could plant and harvest more crops, the larger population begins to starve.
This could provide a lot of new hook: helping revitalize the town could go a lot of different ways, or maybe the villain sweeps in to save them and gets a townfull of people who really don't like the PCs.
Give 'em lackeys
Sherlock Holmes' Baker Street Irregulars come to mind: when someone tips well, he attracts a lot of willing employees. I'd be surprised if some enterprising young urchin didn't pop up to be an eager errand boy. Bonus points if he's got some connection to a plot.
Induct 'em
A high-profile group with plenty of money offers just the kind of publicity and profit many organizations are looking for. Adventuring clubs, philanthropic societies, shady organizations, all would love to have the party as members. Of course, there's an admission fee. And membership dues. And obligations to be fulfilled. But it's very prestigious and members get discounted services at participating locations!
Seriously though, membership can provide access to exclusive quests and resources, an information network, accountants and lawyers to handle the legal issues (see some of the point below), and so forth.
Mug 'em
Clearly these newcomers are rich and naive. Every mugger, pickpocket, cat burglar, confidence man and used car salesman in town is going to see a golden (sorry) opportunity. The party's going to be beset by thieves, get-rich-quick scammers, and people trying to sell them a London Bridge / Eiffel Tower boxed set.
This can provide a lot of interesting action/RP, and maybe even a new adventure: a renowned cat burglar comes to town to steal from the PCs, and the PCs are hired to catch him?
Refuse the coin, call the cops
What's the modern reaction to paying for a stick of gum with a $100 bill? You check if it's counterfeit. If a group of people make a habit of this, the law is going to start making inquiries.
This can go a lot of ways: uncover corruption, make a friend in law enforcement, flee and get a tracker or bounty hunter on their tail.
Note: this is why you see people biting coins in old films. Your teeth scratch off the paint on a fake and show the dark lead underneath. [There's a common misconception that you bite the coin to test its softness, because gold is softer than most other metals. This is incorrect; pure gold coins would wear down just rattling against each other in your pocket, so the gold is always alloyed with another metal to make it harder. If anything, a lead coin (lead was used in counterfeiting because it's about the same weight as gold) would be softer.]
Bring in the bureaucrats
Once the PCs are found to not be counterfeiters, swindlers, or thieves (not necessarily an easy thing to prove, given where most adventurers get their wealth), send in the tax collector and the customs agent. Moving undeclared wealth over borders? Dodging taxes through border hopping or simply not paying? Oh, you say you have no permanent place of residence? Then we'll have to collect your full dues and fines right now, and don't worry; your place of residence for the next six months is the local jail.
Bureaucrats are the nuclear option unless the party likes this kind of thing. Use with caution.
"Those counterfeit coins aren't mine! I got them off this guy I killed... I mean... um."
Seriously, what are the chances that all that junk the party finds in orc pockets is legit? Maybe the cops or the taxmen find something suspicious after all. Or maybe just explaining how they got their wealth is enough to get them in trouble.
See "call the cops" above, but with the added potential for uncovering a new evil plot for the party to stop based on the junk they've been hauling around.
"So that's where they're hiding."
Regardless of how the local population responds, chances are that the party becomes very high-profile very quickly. Is anyone looking for the party? Say... maybe a recurring villain, or someone who wants to set them up as patsies, or a person from a PC's shady past, or someone with a quest for them to undertake?
This is a carte blanche excuse to bring in anyone you want. Be creative: bringing back minor but popular NPCs in a larger role is a favorite of mine.
Best Answer
Well, I hope they're not going into a genuinely random building. Just barging into somebody's house isn't likely to get much in the way of a friendly reaction, but if the PCs say "oh, I want to walk down this street" or "oh, that sounds like an interesting shop" or are otherwise pointing themselves in a sensible direction, and you haven't completely planned what's there? Sure, why not be random?
0) Random For What
But first you should have some idea what you want out of it. Everything you do should reflect off of some goal that either you or the PCs have.
Not just entering some random building for the sake of it, but, you know, looking for something particular to buy, fishing for useful rumors, that kind of thing.
And make sure this isn't something that would be covered just by, say, rolling Discern Realities and asking. Just finding a solid weapon store in an unfamiliar town would certainly be useful or valuable to you, but there's still the question of how the blacksmith is going to feel about you when you get there.
1) Random For How
So, yes, as the GM you never roll dice to make moves. Your antagonists will never be able to roll dice, consult the rules, and just make things happen without the PCs say-so. You can't roll for outcome.
Nobody ever said anything about rolling for intent, though.
That's the purpose of things like the Fourth Page Tables, so named because the stripped-down World of Dungeons version of Dungeon World only had three pages of rules. Need a prompt to keep going? Pick up the City page, roll on Population or Society, and work that idea into the situation that's already established. Or, you know, when you're looking over the list or looking up the die roll, if you see something that speaks to you, you can just use that instead. The purpose of the thing is just to give you ideas, not present some random and absolute balance.
2) Random For Why
But always keep in mind, whatever random prompting method you're using? The players were looking at you to find out what happens. So once you've got your prompt, use that prompt to feed into the GM move you lob back to them.
Let's take the simplest prompt mechanism, the one I'm absolutely sure you will have at your table: The Die Of Fate. Disguised as a humble d6, when you find yourself in need of a prompt, consider a question and roll the Die of Fate for an answer.
So, Die of Fate, is this armorsmith going to be favorably-disposed enough to the PCs to work on their armor?
6: Yes, and. Oh, there's something more? Hmm. Let me offer an opportunity that fits a class's abilities.
5: Yes. Easy enough. Tell them the requirements or consequences and then ask.
4. Yes, but. It can happen right now, but there's a catch. What kind of catch? ...hmm, I think in this case I'll use up their resources.
3. No, but. So it's not an option right now, but it could be. What's in the way? Hmm. I think I'll show signs of an approaching threat.
2. No. Alright. But I don't want to just stonewall them, as much as provide a path forward... ah. I'll reveal an unwelcome truth.
1. No, and. Hmm. I don't want them to get immediately violent, but what can I- ah! Show a downside to their class, race, or equipment.