Penny saved is 10 mills earned

[jeffrey]

A mill of this kind is a coin, worth one-tenth of a penny. Oklahoma is one of several states that issued mills back in the 1930s, for purposes of making change when state sales tax was less than a penny.

Hale: Penny saved is 10 mills earned | Chron.com - Houston Chronicle

[aurielle]

When I was a kid my father gave me some mills from when he was a kid. He grew up in Kansas but I'm not sure if thats where they came from or not.