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 $114.86   10.240%   $126.6217   $126.62   $126.60   $126.60  
  Purchase #2 $207.32   12.562%   $233.3635   $233.36   $233.35   $233.40  
  Purchase #3 $69.63   10.263%   $76.7761   $76.78   $76.80   $76.80  
  Purchase #4 $154.25   11.402%   $171.8376   $171.84   $171.85   $171.80  
  Purchase #5 $146.63   5.438%   $154.6037   $154.60   $154.60   $154.60  
  Purchase #6 $21.48   3.714%   $22.2778   $22.28   $22.30   $22.30  
  Purchase #7 $136.87   8.627%   $148.6778   $148.68   $148.70   $148.70  
  7 purchase totals = $851.04       $934.1582   $934.16   $934.20   $934.20