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 $250.46   4.482%   $261.6856   $261.69   $261.70   $261.70  
  Purchase #2 $67.55   5.107%   $70.9998   $71.00   $71.00   $71.00  
  Purchase #3 $197.33   5.400%   $207.9858   $207.99   $208.00   $208.00  
  Purchase #4 $215.58   11.155%   $239.6279   $239.63   $239.65   $239.60  
  Purchase #5 $149.30   11.258%   $166.1082   $166.11   $166.10   $166.10  
  Purchase #6 $106.90   6.856%   $114.2291   $114.23   $114.25   $114.20  
  Purchase #7 $13.39   5.676%   $14.15   $14.15   $14.15   $14.20  
  7 purchase totals = $1,000.51       $1,074.7864   $1,074.80   $1,074.85   $1,074.80