Gee, you sure were in a hurry but the lack of full stops really mangles what you say.

This is not really a place to ask for homework answers.But I did look at your code and you use a lot of variables like a,b,c etc for what resonable puprose I cant guess.Also code is a bit messed up in the sense that it too packed where you calculate the vals so I could not understant it too much either.

But here's something :
Lesson1:Code clearly and use spaces and newlines.They will save your life when it comes to debugging.Noodle code is a death trap.(Your code is not too noodlely except in the if else part).

Lesson 2:Use funtions (I dont know if you know funtions)

Now your prob:One Idea would be to convert the entire amount in to the lowest denomintions availble(nickle?) and calulate using that.In the end convert it back to dollars and show what ever remanins as nickles.Dont bother with quaters unless you have to.
Not much but i could not understand you code nor what was you prob,nor do i have a compiler handy right now. :0