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 $67.28   13.384%   $76.2848   $76.28   $76.30   $76.30  
  Purchase #2 $148.49   9.189%   $162.1347   $162.13   $162.15   $162.10  
  Purchase #3 $78.69   3.677%   $81.5834   $81.58   $81.60   $81.60  
  Purchase #4 $134.87   9.708%   $147.9632   $147.96   $147.95   $148.00  
  Purchase #5 $245.43   9.354%   $268.3875   $268.39   $268.40   $268.40  
  Purchase #6 $163.59   3.347%   $169.0654   $169.07   $169.05   $169.10  
  Purchase #7 $115.57   12.513%   $130.0313   $130.03   $130.05   $130.00  
  7 purchase totals = $953.92       $1,035.4503   $1,035.44   $1,035.50   $1,035.50