If you use the self-service tills at our local Adsa it goes like this:
You scan an item and the till goes "ping" so you know it has been scanned properly, but before you can do anything you get "Thanks. That's scanned. Please place it in the bagging area". It happens within a nanosecond of every single item. People, many people, have been heard to tell the "woman" in the box to "shut up I'm going as quick as I can!".
So, I fired off an email... as you do. I have just had a phone call from Carl in their tech dept to tell me that they are looking into it and that the timers will be adjusted to give us a bit more time before the "woman" pipes up. 'Every little helps' as one of their competitors often tells us.