If I was one of those employees, my response would be to smile and wave, maybe give a thumbs up, and go back to ignoring them. They can interpret it how they like, and only I know for sure that it means "Lol, you're getting nothing from me, you dumb buttmunch."
I haven't heard that since the Beavis and Butthead days. LOL, thanks for taking me back.
Edit: ROFL... I'm at a bar and right after I posted this comment I saw a sticker on the beer tap. The bar logo here is a woman in a Martini glass and someone made a sticker with that woman's face as (what looks like) Butthead. Perfect timing.