Like this: http://i.imgur.com/uXa4458 :)
It is not about the roughness, just pause the first and the last frame so we can see what is going on :)
It is very rough, I do agree. Had to meet a deadline with it :\
Yeah, it opens and closes too fast, you should add sprites or delay for the chest closed and for the chest opened.
As I see this besides the animation it's well made, but with this fast and unfortunately looped frames it's very rough. Let it open for a few seconds, then close again, or just slow it down a bit. It's just my oppinion but it doesn't look good, and hurts my eyes when I see it.
Wow, I love how the gold looks on the edges!