One of the common uses for such a function is when you need to use a number, which contains a whole "bunch" of places to the right of the decimal, but only use the integer portion in a calculation.
These two functions again assist a report developer to achieve specific rounding requirements when needed for a report.
Some calculations require an integer value rounded in a specific way, and these two functions assist in those situations.
The FIX function is not at all related to RND; its job is to return the integer portion of a number.
No rounding or other data transformation occurs; the function simply cuts off everything to the right of the decimal as shown in the second screen print below.
Items such as random number generation and large scale multiplication give SSRS a great way to achieve results in just a few steps.