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 $143.59   7.674%   $154.6091   $154.61   $154.60   $154.60  
  Purchase #2 $67.98   3.115%   $70.0976   $70.10   $70.10   $70.10  
  Purchase #3 $64.54   6.289%   $68.5989   $68.60   $68.60   $68.60  
  Purchase #4 $76.81   9.306%   $83.9579   $83.96   $83.95   $84.00  
  Purchase #5 $70.71   8.337%   $76.6051   $76.61   $76.60   $76.60  
  Purchase #6 $218.78   8.610%   $237.617   $237.62   $237.60   $237.60  
  Purchase #7 $242.72   4.857%   $254.5089   $254.51   $254.50   $254.50  
  7 purchase totals = $885.13       $945.9945   $946.01   $945.95   $946.00