If you might think your money is yours to do with as you please, you're not quite right. The federal government has a statute that specifically prohibits mutilation, cutting, disfiguring, perforating, and other acts that are intended to make the bills unable to be used. The U.S. Secret Service is responsible for enforcing the law.
Penalties
If you're convicted of defacing U.S. bills or coins, you can face fines, jail time, or both. For bills, the maximum fine is $100 and the maximum jail sentence is six months. For coins, the jail sentence can be up to five years. To be convicted, you must have the intent to defraud someone. For example, the U.S. Mint warns that wearing down edges of coins to make them appear to be error coins -- coins that are incorrectly struck by the U.S. Mint, often rare and popular with collectors -- and then selling them to collectors as error coins constitutes a crime.