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 $162.80   8.137%   $176.047   $176.05   $176.05   $176.00  
  Purchase #2 $249.83   4.690%   $261.547   $261.55   $261.55   $261.50  
  Purchase #3 $53.33   4.837%   $55.9096   $55.91   $55.90   $55.90  
  Purchase #4 $30.74   13.569%   $34.9111   $34.91   $34.90   $34.90  
  Purchase #5 $230.62   8.302%   $249.7661   $249.77   $249.75   $249.80  
  Purchase #6 $140.56   12.106%   $157.5762   $157.58   $157.60   $157.60  
  Purchase #7 $28.60   7.197%   $30.6583   $30.66   $30.65   $30.70  
  7 purchase totals = $896.48       $966.4153   $966.43   $966.40   $966.40