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 $218.81   10.233%   $241.2008   $241.20   $241.20   $241.20  
  Purchase #2 $237.56   7.175%   $254.6049   $254.60   $254.60   $254.60  
  Purchase #3 $245.64   6.456%   $261.4985   $261.50   $261.50   $261.50  
  Purchase #4 $117.34   11.679%   $131.0441   $131.04   $131.05   $131.00  
  Purchase #5 $136.69   13.134%   $154.6429   $154.64   $154.65   $154.60  
  Purchase #6 $158.53   12.415%   $178.2115   $178.21   $178.20   $178.20  
  Purchase #7 $122.73   3.742%   $127.3226   $127.32   $127.30   $127.30  
  7 purchase totals = $1,237.30       $1,348.5253   $1,348.51   $1,348.50   $1,348.40