When you purchase $5 worth of merchandise, you get a 5 cent scrip that can be used for future purchases. $10, 10 cents, and so on. Unfortunately, you can't just buy the scrip at the register - you have to buy merchandise. It's common to find the scrip at Canadian coin shows, priced from about 50 cents to $5 or so.

Most Canadian Tire stores have a bin near the exit where customers can "donate" their scrip for charity. Alas, it has a plexi cover so there's no harvesting.

Other gas stations that once gave out scrip now just print a code on the receipt, taking the fun out of collecting. Like a TITO!