Does a cashier commit embezzlement when she steals from the cash register?

Although you technically could be charged with embezzlement under New York law, it seems unlikely – especially since you were not turned over to law enforcement on the day of the theft.   The store management is probably satisfied to have the money back and you no longer employed there.  However, you should be aware that you did indeed embezzle – you willfully took the store’s money or property without permission, of which you acquired possession lawfully by reason of your employment.

Although New York law lumps embezzlement and larceny together in the same criminal statute, the difference between embezzlement and larceny (theft) is that larceny is the taking of another’s property without the owner’s consent when the thief did not have lawful possession of the property.   If a customer takes money from a cash register, that’s larceny.  When you did it, it was embezzlement.  You could have been charged with grand larceny in the fourth degree (NY Penal Law 155.30), a Class E non-violent felony with permissible sentences for first time offenders ranging probation to up to four years in prison.