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 $199.41   4.644%   $208.6706   $208.67   $208.65   $208.70  
  Purchase #2 $250.45   4.389%   $261.4423   $261.44   $261.45   $261.40  
  Purchase #3 $84.89   13.251%   $96.1388   $96.14   $96.15   $96.10  
  Purchase #4 $133.81   6.725%   $142.8087   $142.81   $142.80   $142.80  
  Purchase #5 $98.48   7.872%   $106.2323   $106.23   $106.25   $106.20  
  Purchase #6 $247.95   11.754%   $277.094   $277.09   $277.10   $277.10  
  Purchase #7 $239.58   8.730%   $260.4953   $260.50   $260.50   $260.50  
  7 purchase totals = $1,254.57       $1,352.8820   $1,352.88   $1,352.90   $1,352.80