How do you feel when you’re asked for a $1 donation when checking out at the supermarket? Do you give? Should you?

No, says Phil Buchanan, author of Giving Done Right: Effective Philanthropy and Making Every Dollar Count. Here’s his rationale:

“Just say no when asked to make a contribution at the cash register, on the phone when it rings at dinner time, or on the sidewalk. Because if you respond just in the moment based on emotion or pressure, you will look back on your charitable contributions and they will feel random and not aligned with whatever thoughtful decision you made about your priorities.

“We all have things we have to do—if your niece is raising money for her school project and asks you to make a contribution, you’re going to do it because it’s your niece. But you’ve got limit that kind of giving if you want to really pursue some goals that are important to you.”

Buchanan’s book also explores giving habits of the uber wealthy and the extent to which they truly understand at a ground level the problems they’re attempting to solve.

Read the MarketWatch interview with the author here.

And next time you’re asked for a buck at the supermarket register, think twice. But give anyway.