tapping a hole - how close does the drill bit have to be
You need a better supplier.

If you use a 7mm drill bit the threads won’t be properly formed and will have less strength. If the load is critical then it might well fail.

For the 3mm instead of 3.3mm you run the risk of breaking the tap off in the hole, which can be a *real pain to remove as the steel used for the tap is very hard.

Engineering suppliers carry an extensive range of drill bits and Zeus tables used to work out drilling and tapping hole sizes.