When I have someone but myself, or the GF working the register, I never ever let them know what the starting amount is in the register, all tickets get reconciled with the tape, and any no-sales must be marked with initials on the tape, and the reason. they also signed an agreement that if the register is short any amount whatsoever, it gets deducted directly from their paycheck.
The cooks were specifically instructed that absolutely no food ever leaves the kitchen without a corresponding ticket, and that all prices must be written on the ticket.
With all of this, I still had a real stupid beotch think she could steal from us without me knowing. Whenever she worked, the register always come up $20-30 short. I had the drawer counted out before we opened, and I counted the drawer after we closed. I left no fudge room.
There are all kinds of tricks pulled in liquor/beer sales that do not require tickets, but very little is available to the thief when it is only food sales.
You can also inventory package drinks, Their are very affordable POS apps available for the iPad, they also come with card processing equipment, did you think of that? If you count your dough balls, weigh your toppings after each shift, and keep a tight inventory, any theft should be caught immediately before it will hurt you.