The assumption is hackers will steal for their own use. The reality is they'll change store inventories of zucchini such that they appear as dragon dildos on the receipt, put 65536 rolls of TP into random victims carts, zero out other people's shopping sessions for the pure hell of it, DOS the vision systems using IR blasters during rush times, frame any customers in uniform (cops, for example) as shoplifters, add negative 2,147,483,648 cans of pepsi to random carts, sign up as username "little bobby; drop table *;" or equivalent, stick RFID tags for embarrassing products to people's shoes so they're billed over and over every time they visit, take things out of and add things to other people's carts when they're not looking, all kinds of fun.
As for plain old physical theft:
Oh here is an interesting exploit. Buy or steal a $20 "VISA gift card" register an account with that as the payment option, walk into the store, grab $500 worth of steaks/liquor, walk out.
I worked at a food store as a starving student and we had interesting problems with people loading up carts and shoving them out the fire safety doors into a waiting pickup truck and driving off. If you allow people with false ID into the building, you will get ripped off. I can assure you police are completely uninterested in video footage of shoplifters, probably due to the near infinite volume. If you can physically get away, unless you achieve felony levels of theft value, you're simply free. This might have interesting long term implications for whats for sale as fewer and fewer people have higher and higher paying jobs and everyone else is perma-poor, such as this tech might scale for 80 pound bags of rice and flour even when almost everyone is poor, but not jars of caviar and $300 bottles of liquor and rare wines and jewelry stores. Salt and pepper, sure, saffron threads probably not.