Not always.
My husband repairs the self-checkouts and had his blackberry stolen while fixing one last week.
Oh my, that stinks.
What I meant was, if an actual purchase is taking place and LP is monitoring the register (they have monitors that show the transaction as it is being scanned, just like the registers do on the floor) and watching the customer bag her items, it would be pretty simple to tell if she were scanning everything she bagged.