I just smile and say “no thank you” and keep going. There’s nothing they can do unless they actually think you stole something and they don’t have the manpower to detain everyone who won’t stop for their receipt check.
Note though that doesn’t apply to Sam’s Club or Costco or similar, if you’re a “member” there you agreed to the checks.
They can’t detain you even if they think you have stolen, though (from a store policy perspective). There’s a reason all these stores train employees “observe don’t interfere”.
Shopkeeper’s privilege does exist, many stores simply choose not to exercise it.
so long as the shopkeeper has cause to believe that the person detained in fact committed, or attempted to commit, theft
Shop keepers privilege can’t be used as a reason to detain customers for a receipt check. They don’t have “cause” as they did not see the person concealing anything.
