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 $46.79   3.569%   $48.4599   $48.46   $48.45   $48.50  
  Purchase #2 $92.86   11.536%   $103.5723   $103.57   $103.55   $103.60  
  Purchase #3 $217.38   10.706%   $240.6527   $240.65   $240.65   $240.70  
  Purchase #4 $177.87   11.165%   $197.7292   $197.73   $197.75   $197.70  
  Purchase #5 $186.63   3.830%   $193.7779   $193.78   $193.80   $193.80  
  Purchase #6 $9.63   5.761%   $10.1848   $10.18   $10.20   $10.20  
  Purchase #7 $149.49   7.341%   $160.4641   $160.46   $160.45   $160.50  
  7 purchase totals = $880.65       $954.8409   $954.83   $954.85   $955.00