I admit I'd never thought of this, but obviously, blind people can't tell a five dollar bill from a fifty dollar bill. Blind people know this, of course, and have successfully sued the federal govt to so something about it:
The U.S. discriminates against blind people by printing paper money that makes it impossible for them to distinguish among the bills' varying values, a federal appeals court ruled Tuesday.
The ruling by the U.S. Court of Appeals for the District of Columbia Circuit upholds a decision by a lower court in 2006. It could force the Treasury Department to redesign its money. Suggested changes have ranged from making bills different sizes to printing them with raised markings.
The American Council for the Blind sued for such changes but the Treasury Department has been fighting the case for about six years.
Vending machine vendors will be angry about this, I imagine.