This all seems a little misguided. All standard dice have opposite sides adding up to the same number and are otherwise evenly distributed, so a bias would have

This all seems a little misguided. All standard dice have opposite sides adding up to the same number and are otherwise evenly distributed, so a bias would have to be quite noticeable to skew the results on average. Dice that tend to roll high/low because of imperfections basically don't exist.