Specifically, don't take $10 even from the drawer every shift. Don't even trust yourself to take a "random" amount between $1 and $20 every shift -- people are shitty at generating random numbers on their own, and audits that are sophisticated enough look for numbers that humans tend to "randomly" select at a disproportionate rate.

I would take nothing every fourth or fifth shift as plausible deniability. On the rest of the shifts, generate a random integer on your phone between 10 and 19, then take that number plus some change. Maybe every now and then take less than $10.

You could do more, but (1) "don't get greedy" is good advice when you're doing anything risky, and (2) don't think in terms of what could get you fired -- because you can get fired for anything -- think in terms of what the cops could prove beyond a reasonable doubt if your boss catches on and tries to do more than just fire you.