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 $96.90   4.859%   $101.6084   $101.61   $101.60   $101.60  
  Purchase #2 $208.34   3.466%   $215.5611   $215.56   $215.55   $215.60  
  Purchase #3 $44.88   5.389%   $47.2986   $47.30   $47.30   $47.30  
  Purchase #4 $136.86   11.206%   $152.1965   $152.20   $152.20   $152.20  
  Purchase #5 $190.73   13.493%   $216.4652   $216.47   $216.45   $216.50  
  Purchase #6 $154.79   12.248%   $173.7487   $173.75   $173.75   $173.70  
  Purchase #7 $124.57   4.603%   $130.304   $130.30   $130.30   $130.30  
  7 purchase totals = $957.07       $1,037.1825   $1,037.19   $1,037.15   $1,037.20