Is there someone with the power to merge tags? If so, I propose merging "macro" and "macros".
More generally, should we prefer singular or plural tags?
Konrad already pointed to the related question in meta.SO. I guess we should keep it the same way, thus plurals should be preferred.
In the beginning it may help to manually merge the tags, by re-tagging some of the questions. As long as there are not that many questions and no moderators, this can help to avoid usage of the wrong tag. It is more likely that people will use existing tags, so re-tagging all questions from macro to macros would lead to higher usage of macros and avoids confusion.
As you may have noticed, I have already merged the macro and macros tag.
In general, I’m for plurals. This is the established usage on Stack Overflow, compare Stack Overflow Meta: tag synonym repository.
Moderators (which will be voted for some time in the public beta, I think?) will have the power to merge tags.