Self Checkouts are not job killers. they still need people to run them. Most stores have 3 SCO clusters that need 3 attendants each per day. thats 9 jobs right there, add in weekend coverage, vacations, part timers, etc and most grocery stores will have a need for around 15 cashiers which is not easy for any store to fully staff.
source: ive worked grocery stores for around 10 years.