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 $60.46   3.210%   $62.4008   $62.40   $62.40   $62.40  
  Purchase #2 $196.29   10.783%   $217.456   $217.46   $217.45   $217.50  
  Purchase #3 $69.30   10.652%   $76.6818   $76.68   $76.70   $76.70  
  Purchase #4 $135.54   9.497%   $148.4122   $148.41   $148.40   $148.40  
  Purchase #5 $78.26   6.150%   $83.073   $83.07   $83.05   $83.10  
  Purchase #6 $220.38   11.485%   $245.6906   $245.69   $245.70   $245.70  
  Purchase #7 $113.76   6.505%   $121.1601   $121.16   $121.15   $121.20  
  7 purchase totals = $873.99       $954.8745   $954.87   $954.85   $955.00