You have to have a number that ends with three zeros. You have to look at the number formed by the last three digits. If this number smaller or equal to 500, you round down, meaning you just replace the three digits by three zeros, if it is bigger than 500, you round up, meaning you replace the three digits by three zeros and add one to the digit of the thousands.
Here, the last three digits form the number 470 which is smaller than 500 so the nearest thousand of 65470 is 65000.