Wrong Prices

I've never noticed before.. (And I love Pick n Pay, so I generally always trust things like these won't happen). But the branch in North Riding has incorrect pricings on numerous items, I've just gone through my slip and example.. The value pack of coke for R57,99 was actually R59,99, and so on. It may seem petty, but my question is... How often has this happened? And whilst, yes it was a couple of rands I was overcharged.. A couple of rands add up very quickly. People need to do their jobs.