I had to buy two items at CVS - a bottle of mouthwash for me and some red yeast rice pills for my wife. I plucked the Listermint from the shelf, took it to the cashier and gave her my phone number and a US$10 bill. The 97cm receipt had just what I was hoping for: a coupon for US$5 (S$6.60) off a purchase of US$15 or more, expiration date three days later.

I headed straight for the vitamin section, where the economy-size house-brand red yeast rice was on sale - buy one for US$22.99, get one free. I brought my two containers to the same cashier, who took the coupon and unjudgingly charged me US$17.99. But wait, there's more. I'd get the equivalent of 2 per cent of that price back in CVS Rewards bonuses for future purchases, and 1.75 per cent in cash via my credit card rewards programme, a total of 67 US cents more to my name.