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 $72.38   5.262%   $76.1886   $76.19   $76.20   $76.20  
  Purchase #2 $169.30   7.874%   $182.6307   $182.63   $182.65   $182.60  
  Purchase #3 $242.59   10.861%   $268.9377   $268.94   $268.95   $268.90  
  Purchase #4 $33.33   4.680%   $34.8898   $34.89   $34.90   $34.90  
  Purchase #5 $245.48   6.618%   $261.7259   $261.73   $261.75   $261.70  
  Purchase #6 $126.96   10.498%   $140.2883   $140.29   $140.30   $140.30  
  Purchase #7 $214.83   11.295%   $239.095   $239.10   $239.10   $239.10  
  7 purchase totals = $1,104.87       $1,203.7560   $1,203.77   $1,203.85   $1,203.70