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 $53.49   13.277%   $60.5919   $60.59   $60.60   $60.60  
  Purchase #2 $225.44   4.145%   $234.7845   $234.78   $234.80   $234.80  
  Purchase #3 $66.38   9.181%   $72.4743   $72.47   $72.45   $72.50  
  Purchase #4 $9.72   13.341%   $11.0167   $11.02   $11.00   $11.00  
  Purchase #5 $51.82   12.336%   $58.2125   $58.21   $58.20   $58.20  
  Purchase #6 $246.78   8.871%   $268.6719   $268.67   $268.65   $268.70  
  Purchase #7 $227.31   6.103%   $241.1827   $241.18   $241.20   $241.20  
  7 purchase totals = $880.94       $946.9345   $946.92   $946.90   $947.00