Doesn't have to be different sized money, though I think that's a good idea in general. (easy to get the bill you want, without having to take them all out)
For the visually impaired, a small symbol for each denomination is enough to assist them. They can feel the symbol and identify the denomination with it.
http://www.snb.ch/n/mmr/tcoreference...sh/source/.swf
Click on 6 for an example.