In my favorite Italian restaurant, very nice place, they are always very polite and when the waiter helps me into the coat when i'm leaving he says: Prego, arrivederci - which i always considered to mean: Thank you, good bye or you are welcome, good bye. Sounds perfect to me.
My answer was "You are welcome, good bye" and was told it should have been "There you go, goodbye", but....when you get to the discussion forum, the answer is stated as "you are welcome, goodbye". Why does this have to be so confusing. There you go, sounds very odd.
Thing is "arrivederci" is a formal (the most formal actually) greeting for when you leave.
I'd render it as "Good day to you sir" or at least "have a good day sir".
Then again it's cultural and depends on the context and I can see how it's hard to render formality in just a word.
Just remember you must use the "Lei" formal you with this greeting or it will just sound awkward.