To round 810 to the nearest ten, you need to look at the digit in the tens place, which is 1. Since this digit is less than 5, you would round down to 810. Therefore, 810 rounded to the nearest ten remains 810.
Oh, dude, rounding 810 to the nearest ten is like a walk in the park. You just look at the digit in the tens place, which is a big ol' 1, and since it's greater than 5, you round up. So, 810 becomes a fancy 820. Like, easy peasy, right?