The $5 fee is payment to mark your exam paper at the end of the course.
You will be awarded a Certificate in Nutrition by OptimalNutrition.Biz for hitting 65% or more & if you get less than 65%, you'll get a Certificate of Completion. If you wish to retake the exam you can but there will be a $5 fee each time for marking your paper.
You can use your Certificate to apply for Insurance to Practice as a Nutritionist.
The title of Nutritionist is a Complementary Therapy related title. In most Countries including the UK, Australia, New Zealand, Canada & many States in the USA the title of Nutritionist is not subject to professional regulation although various Independent Organisations & voluntary overseeing bodies exist.
There is however no Legal requirement to become a member of or associate with these Organisations & Bodies.
Grab yourself a bargain - These courses cost lots more than this!!