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 $249.91   4.826%   $261.9707   $261.97   $261.95   $262.00  
  Purchase #2 $226.28   4.140%   $235.648   $235.65   $235.65   $235.60  
  Purchase #3 $83.33   13.527%   $94.602   $94.60   $94.60   $94.60  
  Purchase #4 $177.49   9.325%   $194.0409   $194.04   $194.05   $194.00  
  Purchase #5 $190.44   13.637%   $216.4103   $216.41   $216.40   $216.40  
  Purchase #6 $125.30   8.471%   $135.9142   $135.91   $135.90   $135.90  
  Purchase #7 $223.83   8.385%   $242.5981   $242.60   $242.60   $242.60  
  7 purchase totals = $1,276.58       $1,381.1842   $1,381.18   $1,381.15   $1,381.10