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 $72.26   3.460%   $74.7602   $74.76   $74.75   $74.80  
  Purchase #2 $24.26   11.741%   $27.1084   $27.11   $27.10   $27.10  
  Purchase #3 $117.36   13.795%   $133.5498   $133.55   $133.55   $133.50  
  Purchase #4 $124.92   9.258%   $136.4851   $136.49   $136.50   $136.50  
  Purchase #5 $238.60   13.682%   $271.2453   $271.25   $271.25   $271.20  
  Purchase #6 $82.48   13.239%   $93.3995   $93.40   $93.40   $93.40  
  Purchase #7 $204.81   8.425%   $222.0652   $222.07   $222.05   $222.10  
  7 purchase totals = $864.69       $958.6135   $958.63   $958.60   $958.60