2009 AMC 10A Problem 2

To get a multiple of $5$ cents, the number of pennies must be a multiple of $5.$ With only four coins, that means using no pennies, but then the four coins are each worth at least $5$ cents, for a total of at least $20$ cents. So $15$ cents cannot be made. The others can: $25 = 10 + 3(5),$ $35 = 3(10) + 5,$ $45 = 25 + 10 + 2(5),$ and $55 = 25 + 3(10).$ Thus, the correct answer is A.