By comparing the decimals, we see that till the thousandths place, the digits are same.
But the digit at the ten-thousandths place in 123.040605 is larger than the digit at ten-thousandths place in 123.040506 and 123.040560.
Now, comparing the remaining two numbers we see that the digit in hundred-thousandths place is smaller in 123.040506.
So, 123.040506 is smaller than 123.040560 and 123.040605.