Profiling sucks. In this case though, I'd say you're simply trading one injustice for another. You go from the ephemeral experience of having a few underpaid lackeys mistrust you, to having an eternal database of everything you buy owned by a third party. Then again, it's getting pretty ridiculous everywhere. The local supermarkets around me - they've gradually stripped real checkout operators away and replaced them…
Lots of people pay by credit card, or use store cards to get discounts. I wonder if it might be worth volunteering that information without any convenience/price reward if it means the shop might somehow act to serve me better as a customer.
I also think self-checkouts are net less degrading than human checkouts. Bag your own groceries. Be trusted enough to say whether those were organic tomatoes and pay the extra few cents. Lower prices and shorter lines are great too.