It would be great to lose the 5 cent, but I see little value in a 20 cent piece (other than collecting another coin). Ten cent, fifty cent, dollar, two dollar coins would be sufficient for me. Maybe reduce the size of the 50 cent piece, which would be sad as it is my favorite coin.
Personally, I would have little use for any denomination above $100, retailers don't like them, people would be suspect in accepting them and for any large purchase I would rather earn the points and 20+ days to earn interest on cash that would otherwise be gone.