Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $68.55   11.148%   $76.192   $76.19   $76.20   $76.20  
  Purchase #2 $51.55   4.635%   $53.9393   $53.94   $53.95   $53.90  
  Purchase #3 $21.47   8.180%   $23.2262   $23.23   $23.25   $23.20  
  Purchase #4 $61.94   11.695%   $69.1839   $69.18   $69.20   $69.20  
  Purchase #5 $57.37   4.860%   $60.1582   $60.16   $60.15   $60.20  
  Purchase #6 $239.68   7.337%   $257.2653   $257.27   $257.25   $257.30  
  Purchase #7 $197.31   4.389%   $205.9699   $205.97   $205.95   $206.00  
  7 purchase totals = $697.87       $745.9348   $745.94   $745.95   $746.00