Always have Correct Change in your wallet

I have always wondered about this.

Always have Correct Change in your wallet: "So 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 nickels, and 4 pennies. With this combination you can produce any number between 1-99 cents. 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."