First, when you say:
German-American
it means your *ethnic" background is German (meaning your ancestors at some time were from Germany), but you were born in America. Or you were born in Germany but now permanantly residing in America.
This should apply to any nation specific usage.
As for:
African-American
this is more general. It could be like "European-American".
Such a person (or their ancestors) would be (or would be perceived to be) from that region of the world. I think we all know the general criteria used, but that is another discussion.
Your sentence is fine and polite as written. I have no grammatical suggestions.
However there may be more diplomatic ways to tell customers that you have included extra charges in the past, but not actually told them about it. This depends entirely on the context.
The general term is charge for costs associated with an item or service. You can charge a customer for the item itself or the service itself, and also charge them additional costs associated with other related expenses.
If you are a company that sends products to people through the mail, then shipping (the cost to send the product) is an expected cost. Sometimes this is referred to as shipping and handling, abbreviated as S&H. It's not uncommon to state the total price for an item, including shipping and handling.
A fee is usually the cost associated with a service of some kind, for example a registration fee, a processing fee, a licensing fee, and so on. Fees may also be penalties for some situation, such as a late fee or a returned check fee. There may be fees associated with the cost of delivering a product, if the delivery requires some kind of special service (an installation fee, for example).
A general way to talk about a document that details the charges in the bill is an itemized bill, or more formally a bill of sale. Less formally you can talk about an itemized receipt, or a breakdown of costs.
So, again as a suggestion:
In the past we included shipping in the total cost of the item, but we have decided to provide an itemized receipt to our customers so they can see a detailed breakdown of the charges.
Best Answer
Both are used and both are acceptable, though you are most likely to hear "that's" rather than "that is/was".
However, "is" cannot be used if the reason, per se, happened in the past.