Trying to do a Row-Total, however I have a percentage in this 'Row-Total' and need it to compute the total percentage and NOT sum it.

Any help would be greatly appreciated!

Use the RECOMPUTE MULTILINES command to accomplish this.

I have a report that sorts by LOCATION,
so, Instead of:
BY LOCATION AS 'Ship Loc'

Try:
BY LOCATION RECOMPUTE MULTILINES AS 'Ship Loc'

This will recompute the percentage for you and not sum it on the total line.