[e2e8]

You can plot out the wire gauges you want on a log scale and then round them to nice whole (metric measurement) numbers. That is in fact what is done for things like fasteners.

[jacobolus]

And then when you try to scale your whole design up, whoops, all the rounding changes and you need to redo everything.

Anyway, neither way here is right or wrong. One optimizes for uniformity of scaling, the other optimizes for intelligibility with a base ten number system.

[arielb1]

It's not like you are making tight fits with wires anyway, a millimeter here or there won't matter.

However, using something like the E12 series would work pretty well.