There are already quite a few Instructables showing how to make origami ninja stars but none that I could find using dollar bills. Though making these with dollar bills is pretty much the same as with paper, there are a few differences so I decided to show how I make them.
Hopefully the pictures and captions explain how to fold these but I've provided written explanation as well. If you can fold them just using the pictures then don't read the text (it's boring) but know that it's there incase you get stuck.
Usually when I make a ninja star I start from the ends of the bill and work in. When I tried to make one out of dollar bills I realized that they have to folded from the center instead because of the different dimension of the bill versus a 1:2 sided rectangle. To get the 1:2 ratio, part of the bill has to be doubled up. I thought of folding this part from the start but I later figured out a better time to do it that provided a fold guide.