You can use the following procedure:
Lets say the name of the textbox for the total at the end is "TextBox_Total_Value"
Add the third column for %age of the total
and enter the expression:
=100*(Fields!Count.Value / ReportItems!TextBox_Total_Value.Value)
and your results will be:
Codes Count %age
Access 2 3.63
Environmental 14 25.45
Local 3 5.45
Other 4 7.27
Owner 24 43.63
Private 5 9.09
Registered 3 5.45
Total 55 100