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 $72.67   5.550%   $76.7032   $76.70   $76.70   $76.70  
  Purchase #2 $200.61   12.836%   $226.3603   $226.36   $226.35   $226.40  
  Purchase #3 $14.54   6.784%   $15.5264   $15.53   $15.55   $15.50  
  Purchase #4 $140.94   4.814%   $147.7249   $147.72   $147.70   $147.70  
  Purchase #5 $166.73   9.496%   $182.5627   $182.56   $182.55   $182.60  
  Purchase #6 $240.47   8.695%   $261.3789   $261.38   $261.40   $261.40  
  Purchase #7 $88.99   3.826%   $92.3948   $92.39   $92.40   $92.40  
  7 purchase totals = $924.95       $1,002.6512   $1,002.64   $1,002.65   $1,002.70