No game recommendations, but I told DD6 we'd go to the bookstore and she could buy a book. She was excited about that and part of the deal was that she had to be able to figure out how much money she'd get back.

We practiced with different amounts of money and different book prices. She used pretend money that she "exchanged" (i.e. turn $5 into $4 and 10 dimes and then into $4, 9 dimes and 10 pennies). This seemed to help her learn borrowing.