I've posted an step by step guide (here) to convert svn in to git including converting svn tags in to git tags and svn branches in to git branches.
Short version:
1) clone svn from an specific revision number. (the revision number must be the oldest you want to migrate)
git svn clone --username=yourSvnUsername -T trunk_subdir -t tags_subdir -b branches_subdir -r aRevisionNumber svn_url gitreponame
2) fetch svn data. This step it's the one it takes most time.
cd gitreponame
git svn fetch
repeat git svn fetch until finishes without error
3) get master branch updated
git svn rebase
4) Create local branches from svn branches by copying references
cp .git/refs/remotes/origin/* .git/refs/heads/
5) convert svn tags into git tags
git for-each-ref refs/remotes/origin/tags | sed 's#^.*\([[:xdigit:]]\{40\}\).*refs/remotes/origin/tags/\(.*\)$#\2 \1#g' | while read p; do git tag -m "tag from svn" $p; done
6) Put a repository at a better place like github
git remotes add newrepo [email protected]:aUser/aProjectName.git
git push newrepo refs/heads/*
git push --tags newrepo
If you want more details, read my post or ask me.