Like someone said---have a lawyer ready. Are there potential witnesses? Cameras? Would anyone else have access to the register? Was there a period of time where you weren't around or in control of the register? When were those times?
When I was in grad school I worked as a manager at a restaurant. We were robbed one night. About a week later I was in desperate need of some new work shoes, and I finally broke down then and bought some. People were giving me the "hairy eyebrow" over that simple actfor about a week. Bullshit! I wasn't involved in an armed robbery!!
Things finally settled down. They never caught the two guys who robbed us, but there was a dishwasher there that I still suspect WAS involved.
I'll never forget having a double-barreled sawed-off shotgun with both hammers pulled back being shoved into my face. NOT a good feeling.
Anyway, if you didn't do it, you didn't do it. They have to prove it beyond a reasonable doubt.