I have a project that needs power. It has both a 328P and an ATtiny85 on it. I have two choices of wall wart here. I can use an old cell phone charger that has a good 5.3V output or I can use an old 12V and regulate it with a 7805. I don't want to use up all that energy in a regulator if I don't have to. Are there any tricks to dropping a little bit of that voltage from the 5.3V to get it under 5V? Maybe a series diode or two? Or would it be safe to just feed the project 5.3V?
That's fine as long as you don't draw more than 200 mA through the 328P and likely less through the Tiny.
What needs so much power? It ain't just those 2 chips.
BTW, regulated 5V USB chargers are pretty cheap if you know how to shop and can wait for delivery.
Otherwise, is the 5.3V regulated? There is a trick called "voltage divider" you can use if it is.