There are many types of romanization. Your Japanese language professor, your linguistics professor, your literature professor and you might all follow a standardized form of romanization that is different from one another. In Professor Seaman's class, she will expect you to use Modified Hepburn romanization. This is also the standard followed by the library. The Kenkyusha dictionary used to be the deciding form of Modified Hepburn until its most recent release when it started using kana instead of romaji :(
What does this mean? Tōkyō not Tookyoo or Toukyou. Shinbun not sinbun or sinnbun or shimbun.
To learn more about the many flavors of romaji, please read the Wikipedia article.