They'd have to redesign cash registers too

dowling duncan US bank note designs
with their vertical format bills, dowling duncan have reignited interest in 'the dollar redesign project'

following description from dowling duncan:

why the size?
we have kept the width the same as the existing dollars. however we have changed the size of the note so that the one dollar is shorter and the 100 dollar is the longest. when stacked on top of each other it is easy to see how much money you have. it also makes it easier for the visually impaired to distinguish between notes.

There's more information at the source, along with closeups of each bill and an explanation for all of them. Conceptual redesigns of common objects are one of my favorite things in the world.