Of course what our audiences can't hear is the chuckling that occurred as we read this question, thinking about what sorts of sites Tom was trying to hide from his coworkers from seeing. In any case the answer to the question is actually important and it depends on which browser you're using.
If you're using Chrome you can use an incognito session. It's an option on the file menu. And when y session is over all the cookies and cache information from that session are removed from the browser. It makes it really easy to clear out the cache when you're done.
Firefox as an option to automatically clear the cache and remove any cookies once you close the browser down.
In Internet explorer there are add-ins to do this for you but we couldn't find a built-in option to automatically not only clear cookies but also your browsing history as you shut down the browser. Altough there might be such an option we didn't find it.
In any case incognito browsing in Chrome, setting in Firefox, and Internet Explorer add-ins will make it possible to completely clear up your browsing history and your cache and your cookies once you're done with your browsing session.