Clear caching for a single entry / tag / template

Hey EE Devs,

Is there anyway to clear the cache for a specific entry / template tag / or page? I found this in the EE code:

if ($PREFS->ini('new_posts_clear_caches') == 'y')
{
    $FNS->clear_caching('all');
}
else
{
    $FNS->clear_caching('sql');
}

Which relates to this method:

function clear_caching($which, $sub_dir = '', $relationships=FALSE)

But how to I determine the sub-directory?

Cheers