Some banks offer this same type of thing when you use their debit card. I have not taken advantage of it since it would probably be a nightmare for keeping track of one's accounts. But the deal is that when you use the debit card for purchases, it automatically rounds up to the nearest dollar and sends the difference to your savings account. If, say, you spend $27.38 at a store, it charges your checking account $28.00. The merchant gets $27.38 and the remaining $0.62 goes into your savings account.

This would work very well for those of us who want to hate carrying cash/change. It's the same concept, although I don't know that all the banks offer it. The advantage here is that instead of loose change sitting in a jar all year, it's in a savings account accruing interest.