Hi Anon,
When you reply, I'm going to move this to the vocabulary section, okay?
Here are some idiomatic ways of asking:
Can I change this hundred into five twenties, please? Can I get five twenties for this hundred, please?
Can you break this dollar into quarters for me? Thanks.
Can you break this twenty into some smaller bills for me, please?
You have a hundred dollar bill, but it's commonly just called a "hundred."