Sometimes, when I go for a pint or when I'm shopping, I find that the workers try to joke around and make comments at me/other customers.
I always sneer whenever they try to do their 'banter'.
In my view, you should simply pay for your product and leave. The only interaction should be this:
Worker: Thank you sir, that'll be (enter amount here) please.
Customer: Certainly (customer pays for product). Bye.
Worker: Bye.
Any deviation from this is cringeworthy, particularly when they try to engage you in their humourless 'banter', which normally involves them saying, 'cheer up/why the long face/you could smile you know/some other stupid comment etc'.