In such situations, I generally either just go straight into my order, which, I'm sure, is what the person is expecting anyway, since he's just been told by his management that he's required to say that, or maybe just say "fine, thanks" and immediately start giving my order.

I stopped feeling guilty about this when one day I realized that at some drive-thrus the initial voice is just a recording so that the person taking the order doesn't actually have to perform that initial interaction with you.

On a related note, and this has mostly gone away, it really irritated me when they would ask if I wanted a particular item as part of the greeting: "Good morning would you like to try a value meal?" That just requires me to say no and then go on to what I wanted to order. Of course, I suppose it might help those people that get to the register after a several minute wait in line and then start deciding what it is they want.