I chose coins because the only times I can remember carrying money out since college was to be able to use it in a vending machine. I may also carry singles for the same purpose, though.
In college, there was no way I was leaving any cash in my room. My roommates were almost overly ethical, but I didn’t know about their friends. That said, one roommate I had kept half of his leftover scholarship money in his room, building up the entire time, and so it was quite a lot of money. (He said that 50% of his money had to go into the church, but he didn’t believe any of the churches he’d been in truly followed God. He instead used his money for missionary supplies, which included bikes for both him and his only convert.)
My family’s last few cars have had change holders. I think they are really cool.