[paulkrush]

It does make sense for dollar coins to hit mainstream as pennies and nickels will disapper before all coins do.

[euroderf]

Nickels won't, because of quarters/dimes math. But yes, the penny tray is freed up.

[dragonwriter]

Maybe quarters also go (perhaps with half-dollars becoming more common, which, alongside dimes and dollars, would give the same first-three-steps scale as penny/nickel/dime, just shifted a decimal place.)