My wife does that
At first I thought that it was from her background in banking, but she said her first husband got her doing it. He did it because he worked in a bookstore and you need to keep the bills organized.
I just cram the bills in there and every once in a while if I have any left, I'll put them in denominational order.
Tom Sinclair
"This is a lovely party," said the Bursar to a chair, "I wish I was here."
-- The Bursar is a man under a *lot* of stress
(Terry Pratchett, Lords and Ladies)