I always either get erroneously told to put item in the bag, or have to take an item out of the bag because for some reason it shouldn't be there according to the register.
For me: When I am doing my weekly food shopping, I just use plastic. When I am grabbing something I forgot or picking up beer or something during the week, I just leave everything in the area, pay, and then bag with my reusables after the fact.
These days I only need human interaction when I buy booze, and that consists of a cashier eyeballing me and approving it.