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 $62.96   5.359%   $66.334   $66.33   $66.35   $66.30  
  Purchase #2 $109.57   6.413%   $116.5967   $116.60   $116.60   $116.60  
  Purchase #3 $71.38   6.788%   $76.2253   $76.23   $76.25   $76.20  
  Purchase #4 $241.96   8.115%   $261.5951   $261.60   $261.60   $261.60  
  Purchase #5 $145.71   11.171%   $161.9873   $161.99   $162.00   $162.00  
  Purchase #6 $206.86   8.452%   $224.3438   $224.34   $224.35   $224.30  
  Purchase #7 $191.79   3.551%   $198.6005   $198.60   $198.60   $198.60  
  7 purchase totals = $1,030.23       $1,105.6827   $1,105.69   $1,105.75   $1,105.60