Always ensure to do a proper screening and background check before hiring a teller.
Always request tellers to provide at least two guarantors, which will be held liable for any theft committed by the teller.
DO NOT share your administrative password with your teller(s)
Always create an account for each teller, and allow them to choose a password known only to them. You should not know their password either.
Creating a teller account for each teller allows you the agency owner or administrator, know who performed which transaction.