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 $97.64   5.487%   $102.9975   $103.00   $103.00   $103.00  
  Purchase #2 $153.88   13.848%   $175.1893   $175.19   $175.20   $175.20  
  Purchase #3 $185.63   10.800%   $205.678   $205.68   $205.70   $205.70  
  Purchase #4 $86.54   6.734%   $92.3676   $92.37   $92.35   $92.40  
  Purchase #5 $95.50   9.355%   $104.434   $104.43   $104.45   $104.40  
  Purchase #6 $67.40   3.508%   $69.7644   $69.76   $69.75   $69.80  
  Purchase #7 $106.62   9.241%   $116.4728   $116.47   $116.45   $116.50  
  7 purchase totals = $793.21       $866.9036   $866.90   $866.90   $867.00