Camera Specs Needed For Cash Register Stations?

A member recently posted this to IPVM Chat:

"Need help with cash register/teller camera(s). Currently they have 5 analog cameras looking at 3' by 3' area. They want me to replace with IP. 15' ceiling height. They want to tell the difference between the currency. I was thinking sticking with box form but trouble figure out the MP and fov for this."

The member said lighting was plentiful and even in the target area.

From a PPF perspective, even a 1080p camera 15' away looking at a 3X3 area gives plenty of density, well in excess of the ~150PPF we noted in our Camera Test: PPF Needed For IDs, Text, Money report.

But what about FPS? What sort of specifications should this camera have?