What is 531,000 rounded to the nearest ten thousand?
When rounding, always START at the place you want to have the final digit. Then move to the right and look at that value. If it is 4 or less, leave the desired place digit as it is. If it is 5 or more, "round it up" to the next higher value.
In this case we want to end up with the 10-thousand place, which is the '3' in 531,000. So, we look to the right, and find a '1'. So, we just retain the '3' and drop the rest.
IF the next digit had been '6' for example - 536,000 - we would have rounded the '3' up to a '4' and obtained 540000 instead.