Here the bell is a social reinforcement for choices and efforts in making a sale; it is conditional on something you did. That something was a complex and extended and learned activity, of the type that few animals other than humans ever exhibit. It shows appreciation and provides an occasion for positive interactions.
This is a far cry from a predictive signal which causes a relatively simple physiological response to occur earlier than it would otherwise, in preparation for some uncontrollable condition.
(Yes, I know I am a very humorless and literal person.)
