For this problem, you don't need to know how much the pencils cost. You're only finding how much the 10 nickels are worth.
Start by knowing how much one nickel is worth. A nickel is worth five cents in US currency. Since you know the worth of one nickel, you can find the worth of ten nickels by multiplying ten nickels by five cents (0.05).
Multiply 10 by 0.05.
10 * 0.05 = 0.5
0.5 is equal to 50 cents in US currency, so this means that Ginger has 50 cents to spend to buy pencils at the school store.