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 $160.75   13.599%   $182.6104   $182.61   $182.60   $182.60  
  Purchase #2 $100.62   6.738%   $107.3998   $107.40   $107.40   $107.40  
  Purchase #3 $48.90   3.829%   $50.7724   $50.77   $50.75   $50.80  
  Purchase #4 $58.71   3.647%   $60.8512   $60.85   $60.85   $60.90  
  Purchase #5 $218.30   12.174%   $244.8758   $244.88   $244.90   $244.90  
  Purchase #6 $72.53   5.161%   $76.2733   $76.27   $76.25   $76.30  
  Purchase #7 $244.27   12.771%   $275.4657   $275.47   $275.45   $275.50  
  7 purchase totals = $904.08       $998.2486   $998.25   $998.20   $998.40