Re: exact change
We use "exact change" as discussed above - If what I purchase is $17.52, I pay with a ten, a five, two ones, two quarters, and two pennies. (Although the 52 cents could be another combination, and I could give the $17 as three fives and two ones, or even 17 ones, etc.) The point is that I give the cashier the exact amount of the sale.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.