Learn English – John is calling you or John’s calling you

A comma after a coordinating conjunction (and, or, but) is only acceptable when the comma is the first of a pair of commas bracketing a ‘supplement’—a phrase or clause which lies outside the main structure of the sentence and interrupts the flow of thought.

  And, as if that were not enough, he went on to sneer at the victim.
     ^---------------------------^  

  But, as you said, there is no point in trying too hard.
     ^------------^

In other circumstances the comma is effectively ‘disjunctive’ and subverts the joining effect of the conjunction.

This counterproductive comma is becoming very common in contemporary business writing; I suspect it represents a hypercorrection by people who have misunderstood the need for commas bracketing supplements, or think it lends formal ‘elegance’ to their writing.

American English.

I would say something costs "ten dollars" which implies "ten dollars and no cents." But it's possible that I'm rounding; in casual speech, and especially when comparing two items at different price points, I might say that a product with a price of $9.88 costs "ten dollars." So to make it clear that the price is really $10.00 I can say "ten dollars even" or "ten dollars flat," emphasizing the fact that there is nothing in the price besides the ten dollars.

When writing the price using Arabic numerals I can use just $10 which (again) implies the absence of any additional cents, or I can explicitly write out the zeros by using $10.00.

Regarding your edit: Using a long dash to indicate "and no cents" ($10— or $10.—) is old-fashioned usage that I have seen more often in the context of handwriting, it being faster to draw a single horizontal line than to mark a zero and another zero. In the era of computers and keyboards I would call that practice obsolete.

I do not think there is standard marking to indicate "a set of prices which will always be an integer number of dollars." You would just have to say it in longform as I did there.