It may be just a SLIGHT thread creep, but where I grew up, (in Perth, Western Australia), if we wanted (e.g.) a ham sandwich - no sorry, I'll make that a VEGEMITE sandwich!! - we'd say :
"one round of Vegemite, thanks" and we'd be given 2 pieces of bread-and-butter, liberally spread with Vegemite (i.e. a sandwich).
Therefore if we wanted 2 sandwiches, we'd ask for "two rounds".

However, once I left the West and tried my luck in the BWW (Big Wide World), people looked at me as if I was daft when I asked for a "round" of something!!!

So my question is : does "a round of" meaning "a sandwich", figure anywhere else in the Western World???

Cheers! R-J