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 $58.27   11.131%   $64.756   $64.76   $64.75   $64.80  
  Purchase #2 $129.30   13.642%   $146.9391   $146.94   $146.95   $146.90  
  Purchase #3 $113.66   11.650%   $126.9014   $126.90   $126.90   $126.90  
  Purchase #4 $242.49   8.264%   $262.5294   $262.53   $262.55   $262.50  
  Purchase #5 $153.97   7.114%   $164.9234   $164.92   $164.90   $164.90  
  Purchase #6 $43.42   12.726%   $48.9456   $48.95   $48.95   $48.90  
  Purchase #7 $116.35   12.249%   $130.6017   $130.60   $130.60   $130.60  
  7 purchase totals = $857.46       $945.5966   $945.60   $945.60   $945.50