Keep in mind the rating on IMDB is constantly changing, so be sure you are looking at the value in your movie.xml file (which could have a different value than what is currently on IMDB).

Also, for your examples...

54/2=27

2.7 rounded to the nearest single digit whole number is 3, so this looks correct.

For the others...

61/2=30.5

3.05 rounded to the nearest single digit whole number is 3, so this seems wrong.

81/2=40.5

4.05 rounded to the nearest single digit whole number is 4, so this seems wrong too.

Like already stated, make sure you are looking at the values in your XML files, not IMDB. If you are looking at the values in the XML files, then this may be a Mede8er scanner bug.