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 $46.76   4.499%   $48.8637   $48.86   $48.85   $48.90  
  Purchase #2 $55.92   11.246%   $62.2088   $62.21   $62.20   $62.20  
  Purchase #3 $229.33   3.317%   $236.9369   $236.94   $236.95   $236.90  
  Purchase #4 $52.72   11.359%   $58.7085   $58.71   $58.70   $58.70  
  Purchase #5 $219.82   5.418%   $231.7298   $231.73   $231.75   $231.70  
  Purchase #6 $111.32   5.332%   $117.2556   $117.26   $117.25   $117.30  
  Purchase #7 $53.59   9.398%   $58.6264   $58.63   $58.65   $58.60  
  7 purchase totals = $769.46       $814.3297   $814.34   $814.35   $814.30