Some stores include a screen for you to accept or decline a charitable donation (with suggested amounts, of course) in their card payment process. One store that has the built-in charity request also has their clerks ask for a bigger donation (purchase a toy for a child, say) as you pile your purchases on the checkout counter. This is manipulative and annoying.

I have encountered the card-reading fund-raisers in front of our local grocery store. I don't mind contributing to the kids for their various projects. What I want in return is for them to articulate what the funds are for and why they need to beg for them. When the kids are eager to explain they receive a donation.