MakeChange for iPad has been available for some time now. It's even been copied.
Over the past couple months I've heard from several educators running pilot iPad programs in their schools. Some are using MakeChange and I've tried to incorporate some of the suggestions into the latest release, which is available starting today at the App Store.
The biggest change has been the addition of foreign currencies; you can now count out Canadian or Euro coins. There's also an option to restrict the usage of the high-value dollar coins if you want to force counting with smaller coins.
More difficulty levels were added to make the app easier to use in classrooms with younger kids. The coins themselves got a bit of a physics makeover. You can slide them across the table now and they'll come to a stop (try sliding some slowly or quickly to see how they differ).
In this screenshot, the currency is formatted for the US. Depending on your locale settings, you should see the appropriate currency symbol in front of your totals.