I've never tried it in the grocery store. I rarely have more than a couple of items when I use self checkout. I was thinking about big box stores where I generally have a bunch of things.
Pat got me thinking.
@ChrisLeicester, where will this be used an by whom? Last time I had to do this was for scanning accountable mail. Had to make sure the user knew to "Wait until it beeps" before they scanned the next item due to lag between "Scan" and "Input to control". If you hit the same problem, you may want to have an audio "Beep" in the after accept for the field to let the user know "You can scan again".