When rounding, always look to the number directly to the right of the number in the place that must be rounded. If the number is 5 or exceeds 5, change the number in the place that must be rounded to one higher number. If nothing exceeds, keep the number as is and change all other preceding places to 0.
In this case, your hundred thousand place would not change because the 3 next to it does not exceed 5.
Therefore, it will be 100,000
Hope this helps :)