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 $113.83   8.591%   $123.6091   $123.61   $123.60   $123.60  
  Purchase #2 $248.35   5.668%   $262.4265   $262.43   $262.45   $262.40  
  Purchase #3 $29.86   7.256%   $32.0266   $32.03   $32.05   $32.00  
  Purchase #4 $241.49   3.369%   $249.6258   $249.63   $249.65   $249.60  
  Purchase #5 $215.88   4.745%   $226.1235   $226.12   $226.10   $226.10  
  Purchase #6 $196.65   8.571%   $213.5049   $213.50   $213.50   $213.50  
  Purchase #7 $94.56   3.694%   $98.053   $98.05   $98.05   $98.10  
  7 purchase totals = $1,140.62       $1,205.3694   $1,205.37   $1,205.40   $1,205.30