This is true. I've also attempted to "exploit" the system by using rounding errors for a bigger edge. Out of many trials, it still fails (what I mean by rounding errors is, for example, finding a sweet number spot where you will actually get slightly more from a win than you should because, for example, you get 1.5 coins instead of 1, which rounds up to a win of 2). Even so, the house always picks up eventually and dominates it.