You should not delete items, or cashiers, or sales reps, or anything from RMS. All of this data is linked together on a transaction, so it's going to cause confusion if you ever want to run reports that are related to the stuff you delete. I usually disable all the "Delete" keys for everybody except the Administrator account.
Items can be marked "Inactive". However it would be nice if Cashiers and Sales Reps had this option as well.
Also, items cannot be "deleted" from a transaction, they are either voided or returned, which is done on a new transaction. And manually adjusting the inventory causes an entry in the item movement history. There is always a trail to follow. It's very difficult for someone to hide their tracks unless they can log in directly to the SQL server (is your sa password set?) and know how and what SQL commands to run.