Depending on why the website "needs" IE, you might be able to get away with a User Agent spoof and not need to pay any money or use a Rosetta program. To do this in Safari, quit Safari and open Terminal to enter the following command:
defaults write com.apple.Safari IncludeDebugMenu 1
Then open Safari and there should be a "Debug" menu option at the top. Click Debug > User Agent > Windows MSIE 6.0 (Or Mac MSIE 5.22) and you should be golden. The same can be achieved in Firefox with a popular extension called Switch User Agent. This will work assuming the only reason you "need" IE is because the website checks to see if you have it. If the website actually requires something from IE, though (dear God, why?), then ignore this post.