Found a flyer at my local Costco for $10 off any $100+ order at Costco.com. I used it today to buy a set of pots and pans and it worked flawlessly.
It looks like all the codes are the same at my Costco so I don't think it's 1 time use. here's the one I used:
There are restrictions like it doesn't work on tires. I'll post full text later when I get home.