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 $48.69   12.366%   $54.711   $54.71   $54.70   $54.70  
  Purchase #2 $195.50   10.347%   $215.7284   $215.73   $215.75   $215.70  
  Purchase #3 $248.67   4.773%   $260.539   $260.54   $260.55   $260.50  
  Purchase #4 $236.61   4.282%   $246.7416   $246.74   $246.75   $246.70  
  Purchase #5 $231.77   12.634%   $261.0518   $261.05   $261.05   $261.10  
  Purchase #6 $15.41   7.488%   $16.5639   $16.56   $16.55   $16.60  
  Purchase #7 $218.32   9.581%   $239.2372   $239.24   $239.25   $239.20  
  7 purchase totals = $1,194.97       $1,294.5729   $1,294.57   $1,294.60   $1,294.50