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 $68.75   5.765%   $72.7134   $72.71   $72.70   $72.70  
  Purchase #2 $221.83   6.656%   $236.595   $236.60   $236.60   $236.60  
  Purchase #3 $76.35   9.389%   $83.5185   $83.52   $83.50   $83.50  
  Purchase #4 $71.57   9.282%   $78.2131   $78.21   $78.20   $78.20  
  Purchase #5 $198.63   4.745%   $208.055   $208.06   $208.05   $208.10  
  Purchase #6 $57.56   9.571%   $63.0691   $63.07   $63.05   $63.10  
  Purchase #7 $195.28   11.227%   $217.2041   $217.20   $217.20   $217.20  
  7 purchase totals = $889.97       $959.3682   $959.37   $959.30   $959.40