On the atmega32u4 datasheet it says:
Can someone explain what those tolerance mean? What if I use parts with lesser tolerance like +/-1%?
It is only an indication. There are different types of resistors and capacitors. Sometimes a metalfilm resistor is needed or a special capacitor with low ESR of a special type of capacitor.
A 5% resistor and a 10% capacitor means just normal components. You can use of course 1% components. That means that the 22 Ω is probably closer to 22 Ω.
±5% means that the 22 Ω can be 20.90 up to 23.10 Ω
±1% means that the 22 Ω can be 21.78 up to 22.22 Ω
Perhaps it will still work when that value is 0 Ω to 120 Ω. But then the specifications in the datasheet are no longer valid.
Guys thank you! That's all i needed to know. 