By Rachel Siegel, Joy Sharon Yi, Hannah Yoon and Emily Wright The Washington Post The $5 bill in your wallet. The $20 bill in the cash register. The $100 bill at the bank. You may be using less cash day-to-day, but some $2 trillion of paper currency keeps the economy churning so that people can exchange, handle and spend money with ease. But wait, does that $20 bill have a tear down the middle? Did someone take a Sharpie to that $100 bill?