I can't believe this thread is still going on, but I'll jump in.
Truth be told, that cashier doesn't give a "rat's behind" whether you contribute or not. She's thinking about what's for dinner, her feet hurt, her kid has a cold, probably many, many things. You are not the center of her Universe.
It's very simple to say "no" or "not at this time" or "I did already" which ever applies.
I personally have two charities I always contribute to. They are reliable and over 95 percent of what they collect actually goes to the charity.
So, if you don't want to contribute, just suck it up and say NO!
