In New Zealand, one of the supermarkets experimented with a self-scanning arrangement. You walked around with a scanner and scanned everything that went into your trolley, you had a running balance available to you and you could remove items after scanning if you decided you didn't want them. Then you would go to a dedicated self-checkout machine and pay for it. They did random checks where you would have to do the full checkout experience of having a checkout operator scan everything like normal, but it was a dedicated checkout so there were no lines. I really enjoyed using it because I could keep track of my spending on the spot, no surprises at checkout.