Based off the advice that I received from poofrabbit, I altered my previous design of the adjustable money clip with a coin that acted as a screw. Now in addition to adjusting to the amount of money that you have, it can also hold coins as well! My old design can be seen at http://www.instructables.com/id/Adjustable-Screw-Money-Clip/. It has detailed SolidWorks instructions on how it was CADed. The last picture shows the original version of this project.
To change this design, I created a third part (the second picture) adjusted the position of the screw so it would fit into this part. I made sure that the coins would fit by using the website http://www.usmint.gov/about_the_mint/?action=coin_specifications to size them. I adjusted the tolerances of both the third part that I created and the space for the coins to ensure that everything would fit together.
I used the exploded view feature on SolidWorks to create the bottom picture.