Managers at my store are getting on my case because I don't 'interact' with customers at the checkout, when I cashier.
I wish the managers would realize that customers don't always care for smalltalk (and that it often makes some of us feel awkward because we feel obliged to chit-chat back and are not chit-chat people), but that'll never happen.
Some good suggestions in this thread. And there's always the "Hope you found everything you needed?" with the question mark on the end so that they can chime in if they didn't (though that may just be Southern-speak, I'm not sure).
There's non-verbal interaction too, smiling, eye-contact (momentarily between every three or four items scanned), etc.
Sometime cashiers will comment on non-controversial type stuff regarding purchases - i.e. someone buying four large bags of candy on October 20th might get a "stocking up for Halloween?" - but I can see how that could be tricky, since you're talking about someone's purchases and some people might not like that. Or the buyer might smile and say "stocking for Halloween" when they put all that on the conveyor belt and then the cashier says "it's that time of year" or something like that.
I guess it comes down to whether the manager thinks you aren't helping the customer enough or the manager thinks a cheery, personable, chit-chatty attitude will make people come back to the store but thinks you're serving the customer fine.
