What coal miner or assembly-line worker jumps at the offer of overtime when he knows Uncle Sam is going to take sixty percent or more of his extra pay?
Look at other large employers who make what Walmart makes and what regular compensation they offer their employees and then the extra compensation they offer for working holidays or overtime, etc.
Often they do that in a shadow economy -- a place where employers may offer them less than the minimum wage or make them work overtime without extra pay.