So my boss just shared this Issue Ticket he just received:

Yesterday 5/20/15 I tried to purchase a monster energy drink for 2.40 in [redacted] cafeteria vending machine. I had all change in quarters, nickels, and dimes. I put 2.40 in the machine and hit the button for the drink. Didn’t come out. I then put 2 quarters in which would have been enough to pay for the drink in all quarters, just in case the machine didn’t take dimes and nickels. Machine still didn’t process by order. So I hit the money return button and got about a dollar back. Not exactly sure how much I put in the machine. However it was between 2.40-3$. I got a dollar back so the machine has roughly 1.40-2 dollars of mine.