Given that the last time Microsoft even pretended to support IE/Mac was when the US federal budget still claimed to run a surplus, I infer the only reason to use IE/Mac instead of Safari,
Firefox, Camino, or Opera et al. is that some site you need to access requires IE.
Bear in mind that if such a site makes use of ActiveX controls, it won't matter if you try IE/Mac; ActiveX is Windows only. However, a large number of sites that require IE do so because the site's programmers were too busy and/or lazy to check their coding was HTML-compliant and work with other browsers. A cheap shortcut to testing the code is to have the site check the browser the visitor is using and refuse anything other than the browser the developer used.
That can be bypassed by having the visitor's browser report that it's actually another browser and even another platform. That can be done by telling the browser to report it's "user agent" identity to be something else, such as IE5/Mac or IE6/Windows (the latter is probably more useful).
You can set the User Agent in Safari by unlocking the Debug Menu. To enable Safari’s Debug Menu, open Applications> Utilities> Terminal when Safari is closed and enter:
defaults write com.apple.Safari IncludeDebugMenu 1
Restart Safari to see the Debug Menu.
Set the User Agent to the desired state just before attempting to go to the site for which you need IE/Mac.
p.s. Welcome to the Apple Discussions!
