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 $82.70   4.357%   $86.3032   $86.30   $86.30   $86.30  
  Purchase #2 $190.65   8.804%   $207.4348   $207.43   $207.45   $207.40  
  Purchase #3 $225.99   13.210%   $255.8433   $255.84   $255.85   $255.80  
  Purchase #4 $229.57   11.340%   $255.6032   $255.60   $255.60   $255.60  
  Purchase #5 $199.65   12.250%   $224.1071   $224.11   $224.10   $224.10  
  Purchase #6 $206.74   5.798%   $218.7268   $218.73   $218.75   $218.70  
  Purchase #7 $169.38   10.448%   $187.0768   $187.08   $187.10   $187.10  
  7 purchase totals = $1,304.68       $1,435.0952   $1,435.09   $1,435.15   $1,435.00