I suspect you can, if there is a bias when no effort is applied I suspect you can train to increase it. I can think of two main factors at play - how fast the coin is rotating and how long it remains in the air. Both of which are under your control and I suspect you can train to become more reliable for though it might take a lot of effort. Or you can just learn to do this in 10 mins. Who is going to know the difference? It is cheating either way.