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 $88.44   8.270%   $95.754   $95.75   $95.75   $95.80  
  Purchase #2 $29.61   9.143%   $32.3172   $32.32   $32.30   $32.30  
  Purchase #3 $6.52   3.141%   $6.7248   $6.72   $6.70   $6.70  
  Purchase #4 $153.46   13.198%   $173.7137   $173.71   $173.70   $173.70  
  Purchase #5 $85.52   8.323%   $92.6378   $92.64   $92.65   $92.60  
  Purchase #6 $199.97   11.226%   $222.4186   $222.42   $222.40   $222.40  
  Purchase #7 $236.43   10.560%   $261.397   $261.40   $261.40   $261.40  
  7 purchase totals = $799.95       $884.9631   $884.96   $884.90   $884.90