I noticed that when I downvote a post then delete it, the vote does not count against my daily voting cap, but I do get credit for having voted. I just keep getting the "You have X votes left today" message. I've voted 70 times on Stack Overflow today, and I could continue as long as I can find posts to delete (not hard).
I think not counting votes on deleted posts is the correct behavior, but those votes should probably also be deducted from my total.
(Note: I recognize that this is an extreme edge case that would be very hard for a non-moderator to exploit, and there's no real gain to be had. "Just stop doing that" is a likely and acceptable response from the dev team.)