For this case we have the following definition:
nearest thousandth: is the second digit of a number after the decimal point
We then have the following number:
7.2199
We note that the third digit after the decimal point is greater than 5.
Therefore, the second digit increases its value by one unit.
We have then that the rounded number is given by:
7.22
Answer:
Rounding to the nearest thousandth we have:
7.22