[mirceal]

don't know about tesco, but I know about Costco. You need to provide your membership card every time you buy. So Costco definitely knows your complete shopping history.

Also any online shop (Amazon included) has a complete history of everything you've ever bought.

For brick&mortar shops you would be a fool to assume they don't mine your shopping history based on your credit card (or some sort of hash that's computed from your CC#).