Jackpot moral dilemma

[Double Down]

Ok, here's a good conversation starter.
You are taking a trip to Vegas. A friend of yours, not a great friend but OK friend, gives you a dollar to play for him in Vegas. You play it for him and you hit a $100,000 jackpot.
If you don't tell him about it, he will never know. What do you do?
What if the jackpot was 1 million? Or 10 million?

Personally, if I won 10 million, I think I'd keep 9 million and give him a million, telling him that that's all there was. I think he'd be pretty stoked and not ask any questions.

Would it make a difference if he was a very good friend?