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 $191.75   5.265%   $201.8456   $201.85   $201.85   $201.80  
  Purchase #2 $70.98   8.282%   $76.8586   $76.86   $76.85   $76.90  
  Purchase #3 $126.68   4.348%   $132.188   $132.19   $132.20   $132.20  
  Purchase #4 $68.66   11.751%   $76.7282   $76.73   $76.75   $76.70  
  Purchase #5 $123.80   7.708%   $133.3425   $133.34   $133.35   $133.30  
  Purchase #6 $136.70   7.124%   $146.4385   $146.44   $146.45   $146.40  
  Purchase #7 $146.95   3.583%   $152.2152   $152.22   $152.20   $152.20  
  7 purchase totals = $865.52       $919.6166   $919.63   $919.65   $919.50