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 $169.46   7.726%   $182.5525   $182.55   $182.55   $182.60  
  Purchase #2 $114.68   10.223%   $126.4037   $126.40   $126.40   $126.40  
  Purchase #3 $247.57   8.636%   $268.9501   $268.95   $268.95   $269.00  
  Purchase #4 $136.78   13.503%   $155.2494   $155.25   $155.25   $155.20  
  Purchase #5 $190.59   9.478%   $208.6541   $208.65   $208.65   $208.70  
  Purchase #6 $155.65   5.558%   $164.301   $164.30   $164.30   $164.30  
  Purchase #7 $136.45   13.256%   $154.5378   $154.54   $154.55   $154.50  
  7 purchase totals = $1,151.18       $1,260.6486   $1,260.64   $1,260.65   $1,260.70