We can split this up into multiple cases to consider.

One-dollar bills: Set up the dividers to get (7-1)C(2)=6C2=15 ways.

Five-dollar bills Again...use the same method to get (6-1)C2=5C2=10 ways.

Twenty-dollar bills: (5-1)C2=6 ways.

Hundred-dollar bills: Any three nephews can get it, so there are three ways or (4-1)C2=3C2=3 ways.

Thus, the answer is 2700 ways.