I've worked fast food a bit - $400 over 4 registers just after a busy period isn't actually all that much, and corporate policy about constantly moving money to the safe is often a 'damned if you do, damned if you don't' policy in that you'll get written up for being too slow if you follow the deposit rules during busy periods.
I was going to say something like that. Skaggs Department store, Chrismas, there was sometimes two hands in the register at once making change. Got to be too full so another peon besides me, with more seniority and experience, grabbed a bunch of cash and stuck the loose bills under the counter.
Closeout time, we were about $10 ahead. You'd think that was a ripe opportunty for a clerk to walk off with a couple of bucks, but nobody did.
I can see a "policy" about that in the OP if you've got a cash drop right by the registers. At Skagg's the manager, in normal times, would come by periodically with a new counted-out drawer, then go back in the office to reconcile the cash in the old drawer with the register sum tape.
Didn't happen in those times when the customer to clerk ratio got too high.
When I had my own store, the safe was way the hell in the back, and I sometimes had to institute a similar measure (stuffing bills behind the counter) to keep the register down to about $50 by guesstimate.
But naturally, at 10:09 AM on one of the first Saturdays after I took over, some turkey came in and bought a 79 cent transistor and offered a $20 bill. Terry smiled, gave him his change, and the first chance, got some more moolah from the safe. So I kept more in the drawer on Saturdays after that.
(I used to leave the drawer open with $50 in it overnight on the theory that someone breaking in would be happy with that and not swipe the whole $2000 register to can-opener it later.)
Terry