any way to apply tag across all branches in repository?

Hi all,

I'm hoping you can help me out...please CC me on replies, I'm not
subscribed to the list.

We have a piece of software with a "main" branch and multiple
architecture-specific "target" branches.  At each "official" compile,
we'd like to tag the commits that went into that compile with an identifier.

Using tags normally requires that the tag be assigned to each branch
individually--is there any way to apply some sort of designator to the
head of each branch in the repository all at once rather than doing it
separately for each branch?

Thanks,

Chris