This. https://aus.social/@[email protected]/111958800765737876
When you "round up your total and donate to charity", the company is using your money to give themselves a tax break, rather than putting their own money to charity for their tax break.
You get all of the cost, they get all of the benefit.
Never do those. Save the money and make your own charity donations at a later time. Get your own tax break from it.