Now. There are a variety of reasons you might not want to do it anyways. I do not want to donate to my local police fund, for instance, and sometimes their choices of who the money goes to are pretty sketchy. Sometimes they are great, sometimes not
So it isn't just a "oh absolutely always round up!"
But the reason to do it or not do it is because you don't want to donate the ($0.37 or whatever) to that charity
Not because the company is taking a tax writeoff for your donation instead of you