1) Pay your taxes, douche.
2) Haven't you ever heard of Neteller?
3) Can you really imagine the guy at customs going "hay, it ain't drugs, but it's a check! Let's report it to the IRS!"
4) Can you really imagine the guy at the IRS going "O RLY, you saw that Joe Schmoe got a check?? Great, we'll write it down and git 'em if he doesn't report it!"