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 $69.63   9.508%   $76.2504   $76.25   $76.25   $76.30  
  Purchase #2 $103.66   9.644%   $113.657   $113.66   $113.65   $113.70  
  Purchase #3 $141.41   5.433%   $149.0928   $149.09   $149.10   $149.10  
  Purchase #4 $244.99   6.775%   $261.5881   $261.59   $261.60   $261.60  
  Purchase #5 $208.31   11.759%   $232.8052   $232.81   $232.80   $232.80  
  Purchase #6 $233.95   12.355%   $262.8545   $262.85   $262.85   $262.90  
  Purchase #7 $176.72   9.228%   $193.0277   $193.03   $193.05   $193.00  
  7 purchase totals = $1,178.67       $1,289.2757   $1,289.28   $1,289.30   $1,289.40