Which of the following is the best argument for keeping the penny in circulation in the United States?

a. It helps when adding sales tax, which often includes fractions.
b. It has the face of a very accomplished president.
c. It costs more than a penny is worth to manufacture one.
d. It would help marketing to have every price end in a 0 or 5.

a. It helps when adding sales tax, which often includes fractions.