Can I create a display that contains a food menu that updates the database after each sale?

You sure can.  I played around with a "point of sales" application / idea for a while...  Was going to link it to a register / printer so it could pop open a cash drawer..   Never really got it off the ground..  But it is more than possible... :) 

I use Ninox as a cannabis seed to sale tracking solution. It is a legal requirement for me.

Part of my solution is a shared view that is the “in stock” menu.

@blackie... "cannabis seed to sale".... I knew I liked you for some reason.. LOL  Best of success to you. 

In relation to POS and popping a cash register is this possible?

@Scott ... most set ups that I am familiar with use the thermal printer to trigger the drawer to open.   So when a receipt it printed, it pops the drawer.   I suspect there may be other "api" or "device" driven set ups..   The down side.. this adds an extra step as Ninox will first "print to PDF" ...   And.. for the API / device driven.. I think it would have to be a REST/API.    

As I previously indicated.. I never took the application beyond the concept phase.. so I would be interested in hearing how others have solved this.