Manager does nothing about slacking co-workers

I need advice concerning my workplace, I work in retail and my co workers are not organized at all because well, management does not care, simple as that (third world bs) anyways, when it is "prayer time" they don't warn me or anything, they go and do their prayers and I am left alone to deal with like 4-5 customers which is frustrating, I complained to my manager yesterday, I even told them that they all left at the same time which is unfair to me. Not to mention that praying takes like 5-10 mins, some of them leave for like 40-50 minutes like what the fuck.