Blind shoppers sometimes need an easy method for identifying currency in their wallets. Here is one system that works well. The AFB Senior Site suggests folding denominations of bills in different ways so you can easily find them: 
Leave $1 bills unfolded.
Fold $5 bills by width.
Fold $10 bills lengthwise.
Fold $20 bills lengthwise and then by width.

 For more information and other helpful hints, visit AFB Senior Site.