You're using cent_amount again and again, without updating. I think you meant to use something else instead at those places I've marked below:

quarter_amount= cent_amount / QUARTER;
leftover_amount= cent_amount % QUARTER;

dime_amount= leftover_amount/ DIME;
leftover_amount= cent_amount % DIME;

nickel_amount= leftover_amount/ NICKEL;
leftover_amount= cent_amount % NICKEL;

You're using cent_amount again and again, without updating. I think you meant to use something else instead at those places I've marked below:

quarter_amount= cent_amount / QUARTER;
leftover_amount= cent_amount % QUARTER;

dime_amount= leftover_amount/ DIME;
leftover_amount= cent_amount % DIME;

nickel_amount= leftover_amount/ NICKEL;
leftover_amount= cent_amount % NICKEL;

EDIT: Then you'll also have a problem with float imprecision, which will need the round() function. But let's leave that for another question.

Tell me if my answer to this guy's question also answers your question. If not, I'll elaborate:

You're using cent_amount again and again, without updating. I think you meant to use something else instead at those places I've marked below:

quarter_amount= cent_amount / QUARTER;
leftover_amount= cent_amount % QUARTER;

dime_amount= leftover_amount/ DIME;
leftover_amount= cent_amount % DIME;

nickel_amount= leftover_amount/ NICKEL;
leftover_amount= cent_amount % NICKEL;