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 $240.57   8.672%   $261.4322   $261.43   $261.45   $261.40  
  Purchase #2 $230.96   3.646%   $239.3808   $239.38   $239.40   $239.40  
  Purchase #3 $42.99   8.706%   $46.7327   $46.73   $46.75   $46.70  
  Purchase #4 $42.31   4.155%   $44.068   $44.07   $44.05   $44.10  
  Purchase #5 $87.27   10.725%   $96.6297   $96.63   $96.65   $96.60  
  Purchase #6 $237.39   9.794%   $260.64   $260.64   $260.65   $260.60  
  Purchase #7 $148.81   5.136%   $156.4529   $156.45   $156.45   $156.50  
  7 purchase totals = $1,030.30       $1,105.3363   $1,105.33   $1,105.40   $1,105.30