Finding constants of an equation from a graph?

Hello

I have a transfer function that I'm trying to relate to another equation to get some constants. To make this more clear, I will show you an example. My transfer function is :

(-0.7312 s^4 - 0.795 s^3 - 8.145 s^2 + 10.92 s + 28.8)/
( 3.811 s^6 + 66.06 s^5 + 717.1 s^4 + 6787 s^3 + 28690 s^2 + 12750 s + 9.6)

and the constants I want to find are in this equation:

 (Ke^(-t_d S))  / (τs+1)

So What I've been doing is drawing these two lines on a graph and through trial and error, trying to find the constants that would make the graphs almost identical. Is there a better way to do this? I'm going to write my code below if anyone's interested to check over it.

%Actual and Approximate TFs Response
NumA=[-0.7312 -0.795 -8.145  10.92 28.8];
DenA=[3.811  66.06  717.1 6787 2.869e04 1.275e04 9.6];
% Actual Transfer Function
Actual=tf(NumA,DenA);
Actual
num2=[3];
den2=[0.7,1];
% Approximate Transfer Function
Approximate=tf(num2,den2,'InputDelay',0.1);
% Plotting Actual and Approximate Transfer Functions
t=0:0.1:100000;
step(Actual,t)
hold on
step(Approximate,t,'r')
hold off
axis([0 100000 0 10])

Thank you in advance