I've never worked at a brick & mortar retailer, so I can't know for sure. I know for sure that online retailers do this - a few have been caught showing different prices to different customers, or to the same customer in different browsers. I'd be very surprised if Walmart/Target/Safeway/CVS/etc. don't - what else is the point of the "rewards card" if not to gather detailed data? Why do they seemingly have a different "everyday low price" every month?