Disagree. And I disagree speaking from experience as a former drug store shift manager. Yes, I hated that job and it sucked (well, actually it was awesome with the exception of dealing with the public). I pulled rank occasionally on annoying customers, but I was never in the right. Yes, some customers often try to get something for nothing, but this situation is one of two things. Either the signs are clearly marked that you can't mix and match (which I assume they aren't since the manager never seemed to point that out), or they are purposefully deceptively marked, hoping people buy three different candies, but pay full price, or the computer system is miss programmed so the discount isn't given. If it is either of the latter situations, the manager needs to pucker up and kiss butt, because that is what his job is, regardless of how much he hates it. He doesn't like it? He can find some other way to make a living.