I’m doing better now, but 15 years ago Walmart was the only option I had for food. Local/regional grocery stores were more expensive and I was living paycheck to paycheck with growing debt.
“If people were smart they would stop buying the most cost-efficient option” is really not feasible.
“If people were smart” they would read and stop putting oligarchs in power.
I rarely recognize the charities they sponsor, and I don’t exactly trust McDonalds and Walmart to have the same values as me when they select charities. So no, I don’t ever round up. I try to do my due diligence in researching, and I donate on my own.