The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$1.789\mid2$

Now consider the first digit of the second part: It is a 2, so you round down.

$1.789$

The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$13.271\mid5$

Now consider the first digit of the second part: It is a 5, so you round up.

$13.272$

The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$34.576\mid834523$

Now consider the first digit of the second part: It is a 8, so you round up.

$34.577$

The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$8.872\mid487$

Now consider the first digit of the second part: It is a 4, so you round down.

$8.872$

The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$5.619\mid8$

Now consider the first digit of the second part: It is a 9, so you round up. Be careful: Since you round up a 9, you have to adjust also the digits to the left of it (from 1 to 2).

$5.620$

The number is to be rounded to three decimal places. To do this, divide the number into two parts:

1. the part that ranges from the left until the place to which you should round

2. the part containing all other digits on the right of it

$98.999\mid8$

Now consider the first digit of the second part: It is a 9, so you round up. Be careful: Since you round up a 9, you have to adjust also the digits to the left of it (from 899 to 900).

$99.000$