Is it a wobbly fish tank?

I got a tetra 10 gallon fish tank from Wal-mart and I take it home and put it on my dresser and it wobbles so I put it on my night stand and it still wobbles, I then put it on my brothers dresser and it doesn't wobble. I put a level on my dresser and it's level so i'm wondering is it the fish tank that is uneven or the dresser? I'm also worried it could be my floor because I have carpet. I want to get a stand but I don't know what stand would be cheap but also good on carpet and well balanced for a 20 gallon because I am taking it back and getting a 20 gallon tank. Any suggestions please.