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 $116.76   4.862%   $122.4369   $122.44   $122.45   $122.40  
  Purchase #2 $96.33   13.836%   $109.6582   $109.66   $109.65   $109.70  
  Purchase #3 $14.86   5.857%   $15.7304   $15.73   $15.75   $15.70  
  Purchase #4 $108.84   12.748%   $122.7149   $122.71   $122.70   $122.70  
  Purchase #5 $124.90   7.724%   $134.5473   $134.55   $134.55   $134.50  
  Purchase #6 $162.66   6.299%   $172.906   $172.91   $172.90   $172.90  
  Purchase #7 $198.38   9.703%   $217.6288   $217.63   $217.65   $217.60  
  7 purchase totals = $822.73       $895.6225   $895.63   $895.65   $895.50