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 $48.76   12.699%   $54.952   $54.95   $54.95   $55.00  
  Purchase #2 $111.39   3.149%   $114.8977   $114.90   $114.90   $114.90  
  Purchase #3 $170.30   11.573%   $190.0088   $190.01   $190.00   $190.00  
  Purchase #4 $23.27   13.564%   $26.4263   $26.43   $26.45   $26.40  
  Purchase #5 $76.68   6.228%   $81.4556   $81.46   $81.45   $81.50  
  Purchase #6 $26.39   3.294%   $27.2593   $27.26   $27.25   $27.30  
  Purchase #7 $206.63   5.781%   $218.5753   $218.58   $218.60   $218.60  
  7 purchase totals = $663.42       $713.5750   $713.59   $713.60   $713.70