I don't believe in giving gifts for the sake of obligation. That being said, if you're doing it from the mindset of withholding a "reward", I don't think that's a good idea.
I didn't get the impression that you were trying to punish him, more that you're just so hurt that giving a gift would feel like a lie because your heart's not behind it. I could be wrong, that's just what I got from your posts.
I wouldn't buy a gift for someone unless I truly wanted to, I hate anything fake.