Enable Safari's Develop menu, then choose a user agent that placates whatever ill-conceived webpage you need to use.
If that does not work try Firefox. Some websites that render oddly in Safari might work with Firefox. Firefox has plugins that allow you to specify the user agent in the same manner - here is one:
Then tell your employer's IT geniuses that requiring a specific browser is short-sighted, and requiring IE for anything any more is profoundly stupid.