Ditto Elbert's comment. My own experience was long ago - we opened a bar in Northern California in the 70's. The bank was 1/2 block away and had a night drop. The closing bartender dropped off the cash receipts each night after locking up. It took about 2 weeks from the day we opened for somebody to stick the poor guy up, handcuff him to a urinal, and take the cash. That was in a sleepy, affluent town where nobody locked their doors and the cops drove drunks home and put them to bed instead of arresting them.
We just didn't see it coming.
More important than weaponry, is an unpredictable schedule for deposits and a minimum of cash on hand.