This would require a backend change most likely - but when scanning things in checkout, it would be extremely helpful if you could scan items in and immediately go to the next line without having to wait for the system to find the first item in the database.

If a person hits enter to go to the next line at checkout, it could continue searching for the previous item in the background while allowing sequential entries. I've used web-based envision before and it would show small loading bars under previously entered items until it finds them, but wouldn't stop you from inputting more.