"Have a good day" would just as equally and politely close the interaction while not implying you were just assisted with a social debt.
I agree and I use that all the time.
Even if "thank you" acknowledges a social debt then you're not indebting the cashier by thanking them. Being told you're welcome implies that you owed the cashier when they simply did their job.
Anyway, apparently I'm in the minority on this and that's fine!
