It seems to me that French culture finds a pretty happy medium between the two extremes: you aren't expected to engage in a "full" conversation asking how the other's day is, but a simple "bonjour monsieur/madame" and "merci monsieur/madame, au revoir" is more than sufficient.
To me this is the optimal point between being sincere and being socially cordial with a stranger, especially one whose shop you have just entered to do business.
I also like German - an interaction with someone at a store is littered with danke and bitte, but if you ask someone how they are, you actually mean it.
To me this is the optimal point between being sincere and being socially cordial with a stranger, especially one whose shop you have just entered to do business.