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 $182.32   5.833%   $192.9547   $192.95   $192.95   $193.00  
  Purchase #2 $14.85   3.783%   $15.4118   $15.41   $15.40   $15.40  
  Purchase #3 $199.49   4.548%   $208.5628   $208.56   $208.55   $208.60  
  Purchase #4 $208.49   11.591%   $232.6561   $232.66   $232.65   $232.70  
  Purchase #5 $201.63   6.584%   $214.9053   $214.91   $214.90   $214.90  
  Purchase #6 $185.99   10.445%   $205.4167   $205.42   $205.40   $205.40  
  Purchase #7 $209.89   12.672%   $236.4873   $236.49   $236.50   $236.50  
  7 purchase totals = $1,202.66       $1,306.3947   $1,306.40   $1,306.35   $1,306.50