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 $219.83   7.626%   $236.5942   $236.59   $236.60   $236.60  
  Purchase #2 $45.81   13.650%   $52.0631   $52.06   $52.05   $52.10  
  Purchase #3 $211.40   7.806%   $227.9019   $227.90   $227.90   $227.90  
  Purchase #4 $13.39   10.355%   $14.7765   $14.78   $14.80   $14.80  
  Purchase #5 $240.41   8.689%   $261.2992   $261.30   $261.30   $261.30  
  Purchase #6 $162.66   9.730%   $178.4868   $178.49   $178.50   $178.50  
  Purchase #7 $10.51   7.621%   $11.311   $11.31   $11.30   $11.30  
  7 purchase totals = $904.01       $982.4327   $982.43   $982.45   $982.50