Is Winrar’s “store” mode the same as tar

Both tar and cpio have a single purpose: concatenate many separate files to a single stream. They don't compress data. (These days tar is more popular due to its relative simplicity – it can take input files as arguments instead of having to be coupled with find as cpio has.)

In your case, you do not need either of these tools; they would have no useful effect, because you don't have many separate files. zfs send already did the same thing that tar would have done. So you don't have any files, only a nameless stream.

To compress the snapshot, all you have to do is pipe the zfs output through a compression program:

zfs send media/mypictures@20070607 | gzip -c > ~/backups/20070607.gz

gzip -dc ~/backups/20070607.gz | zfs receive media/mypictures@20070607

(You can substitute gzip with xz or bzip2 or any other stream-compression tool, if you want.)

tar tf archive.tar

will list the contents line by line.

This can be piped to xargs directly, but beware: do the deletion very carefully. You don't want to just rm -r everything that tar tf tells you, since it might include directories that were not empty before unpacking!

You could do

tar tf archive.tar | xargs -d'\n' rm -v
tar tf archive.tar | sort -r | xargs -d'\n' rmdir -v

to first remove all files that were in the archive, and then the directories that are left empty.

sort -r (glennjackman suggested tac instead of sort -r in the comments to the accepted answer, which also works since tar's output is regular enough) is needed to delete the deepest directories first; otherwise a case where dir1 contains a single empty directory dir2 will leave dir1 after the rmdir pass, since it was not empty before dir2 was removed.

This will generate a lot of

rm: cannot remove `dir/': Is a directory

and

rmdir: failed to remove `dir/': Directory not empty
rmdir: failed to remove `file': Not a directory

Shut this up with 2>/dev/null if it annoys you, but I'd prefer to keep as much information on the process as possible.

And don't do it until you are sure that you match the right files. And perhaps try rm -i to confirm everything. And have backups, eat your breakfast, brush your teeth, etc.