Currently there are some tags ce-1.7, ce-1.7.22, ee-1.12 and so on.
I think it would make sense to limit this to the second-point releases as the last-point releases (such as 18.104.22.168) usually do not change so much.
I think tagging is good, and why not have a tag for ce-22.214.171.124 and one for ce-1.7 and if you use 126.96.36.199 just use both :)
I personally prefer to have a full version in a tag. It removes any additional questions for a version clarification.
I'd go with only the edition (community or enterprise) and then only the first 2 values of the release.
@Tim has a point in 1.3.x.x and 1.4.x.x but those are only exceptions to the general rule.
And I don't dare say those are obsolete versions but they are becoming rarer