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 $218.66   3.705%   $226.7614   $226.76   $226.75   $226.80  
  Purchase #2 $243.45   7.486%   $261.6747   $261.67   $261.65   $261.70  
  Purchase #3 $26.53   3.596%   $27.484   $27.48   $27.50   $27.50  
  Purchase #4 $239.25   3.734%   $248.1836   $248.18   $248.20   $248.20  
  Purchase #5 $248.97   5.411%   $262.4418   $262.44   $262.45   $262.40  
  Purchase #6 $63.25   13.838%   $72.0025   $72.00   $72.00   $72.00  
  Purchase #7 $196.80   9.684%   $215.8581   $215.86   $215.85   $215.90  
  7 purchase totals = $1,236.91       $1,314.4061   $1,314.39   $1,314.40   $1,314.50