Fewest number of coins to produce exact change

What is the fewest number of coins you can carry that allows you to produce any exact change?
The answer is 10 coins, 3 Quarters, 1 dime, 2 nickel, and 4 pennies. With this combination you can produce any number between 1-99 cents.
3 Quarters
1 dime
2 nickels
4 pennies

An alternative answer would be 6 coins, 3 Quarters, 2 dimes and 1 nickel. In this example you will range most change between 5-95 cents, in 5 cents increments. In this example you will never receive more than 4 cents in change back.

Seven US coin version: four pennies, two nickels, one dime.
Then, you give only as much change as is over the nearest multiple of quarters.
So, for example, if the charge is $12.38 you pay $20.13, and get $7.75
Your change back will always be in multiples of 25.

http://www.instructables.com/id/
Always-have-Correct-Change-in-your-wallet/