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 $179.44   9.414%   $196.3325   $196.33   $196.35   $196.30  
  Purchase #2 $105.30   11.348%   $117.2494   $117.25   $117.25   $117.20  
  Purchase #3 $115.69   8.857%   $125.9367   $125.94   $125.95   $125.90  
  Purchase #4 $243.84   7.183%   $261.355   $261.36   $261.35   $261.40  
  Purchase #5 $241.92   5.522%   $255.2788   $255.28   $255.30   $255.30  
  Purchase #6 $37.65   12.650%   $42.4127   $42.41   $42.40   $42.40  
  Purchase #7 $148.90   9.438%   $162.9532   $162.95   $162.95   $163.00  
  7 purchase totals = $1,072.74       $1,161.5183   $1,161.52   $1,161.55   $1,161.50