Common cents for your pre-schooler. Dollars, dimes, and quarters, too!
Learning Resources Teaching ATM Bank ($29.99) is a modern take on the traditional play cash register. Unlike the one's you may have used as a kid, this one has a battery that powers a small computer that provides some electronic fun, but what I like about it best is the non-augmented, traditional pretend play it sparks. At its heart, this toy is (as the name says) a bank. You can use the pretend coins that it comes with or even use real quarters, dimes, and nickels for your "deposits". Bet you can't do that on your ATM! The computer keeps a tally of the change you deposit, recognizing the sizes of the various coins.
Unlike your ATM, this one doesn't spit out bills. Instead you can roll in pretend dollars into the till. Unlike the coins, the bills are not automatically registered, but kids can have fun adding the dollar amounts manually with the ATM keyboard.
It comes with a pretend debit card, and kids can enter a pin code, just like mom and dad. Marked 3&up, but will probably be more fun for kids already learning arithmetic and money, say 5-7 year olds.
The same company makes a similar cash register. If you prefer that play pattern better (minus the automated coin counting, for instance) as of this writing it was about five dollars cheaper.