No, they don't. This, and the related idea that they're doing it for a tax benefit, are myths.
https://apnews.com/article/fact-checking-000329849244
"Rather than receiving a customer’s donation as income, the company serves as a holding agent for that money, Zaretsky said. Customers may tally up their cash register donations for their own tax returns, but stores are not allowed to claim those."
I went and check. Doesn’t seems so. 0% for charitable organizations (which means they loose money as they need to cover payment processing fees) and less than 2% in most cases for personal ones (which seems to be in line with general payment fees).
https://www.facebook.com/help/901370616673951
Are there any other fees they don’t tell us about there?
The marketplaces that are entirely charitable stuff have to charge or source (they often have a checkbox you can use to "donate" to cover the fees, so you give $10.30 instead of $10 so the charity gets $10).
https://thegrocerystoreguy.com/why-do-grocery-stores-ask-for...
Tiktok is just the long arm of the CCP.
If you want to help, support your local independent stores and avoid the chains. I know that's not practical for everyone and can be more expensive but better conditions for workers doesn't come cheap.
Unless you take them out of the bloated salaries and perks of upper management...
You can do much more for retail workers as a customer by not being an ass and by doing things like putting things back where you found them instead of leaving eggs in amongst the produce, etc.
Thankfully, it appears, according to another responder that they're not taking chunks of money out of these donations and they're getting to the charities.