Perhaps this —
s = tf('s');
G = (7507.852*s^3 - 37030.228*s^2 - 70479.368*s + 100001.744) / (s^5 + 50*s^4 + 1000*s^3 + 10000.585*s^2 + 9997.664*s + 10001.744);
figure
stepplot(G)
grid
s = stepinfo(G)
Settling_Time = s.SettlingTime
From the documentation:
By default, SettlingTime measures the time it takes for the error to stay below 2% of |yfinal – yinit|.
That would appear to meet your requirement for it.
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