80
You would round it down... to 80.
80
80
80
80
80
80
80
Well, darling, 75 rounded to the nearest 10 is 80. It's not rocket science, honey. Just bump that 5 up to the nearest 10 and call it a day.
75 rounded to the nearest ten is 80
Well, darling, the least number that rounds to 80 when rounded to the nearest 10 is 75. You see, when you round 75 to the nearest 10, it becomes 80. So, there you have it, simple math for a simple question.