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 $214.99   12.406%   $241.6617   $241.66   $241.65   $241.70  
  Purchase #2 $57.85   8.351%   $62.6811   $62.68   $62.70   $62.70  
  Purchase #3 $207.52   8.259%   $224.6591   $224.66   $224.65   $224.70  
  Purchase #4 $229.89   13.840%   $261.7068   $261.71   $261.70   $261.70  
  Purchase #5 $101.69   8.410%   $110.2421   $110.24   $110.25   $110.20  
  Purchase #6 $52.51   13.189%   $59.4355   $59.44   $59.45   $59.40  
  Purchase #7 $208.44   3.699%   $216.1502   $216.15   $216.15   $216.20  
  7 purchase totals = $1,072.89       $1,176.5365   $1,176.54   $1,176.55   $1,176.60