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 $237.44   10.274%   $261.8346   $261.83   $261.85   $261.80  
  Purchase #2 $217.32   8.438%   $235.6575   $235.66   $235.65   $235.70  
  Purchase #3 $224.65   5.763%   $237.5966   $237.60   $237.60   $237.60  
  Purchase #4 $90.32   6.554%   $96.2396   $96.24   $96.25   $96.20  
  Purchase #5 $239.55   4.782%   $251.0053   $251.01   $251.00   $251.00  
  Purchase #6 $112.37   4.657%   $117.6031   $117.60   $117.60   $117.60  
  Purchase #7 $216.70   8.769%   $235.7024   $235.70   $235.70   $235.70  
  7 purchase totals = $1,338.35       $1,435.6391   $1,435.64   $1,435.65   $1,435.60