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 $248.92   5.303%   $262.1202   $262.12   $262.10   $262.10  
  Purchase #2 $38.87   8.766%   $42.2773   $42.28   $42.30   $42.30  
  Purchase #3 $223.71   4.763%   $234.3653   $234.37   $234.35   $234.40  
  Purchase #4 $119.51   11.189%   $132.882   $132.88   $132.90   $132.90  
  Purchase #5 $104.61   3.459%   $108.2285   $108.23   $108.25   $108.20  
  Purchase #6 $238.25   3.426%   $246.4124   $246.41   $246.40   $246.40  
  Purchase #7 $180.49   3.474%   $186.7602   $186.76   $186.75   $186.80  
  7 purchase totals = $1,154.36       $1,213.0459   $1,213.05   $1,213.05   $1,213.10