if 3.50 refers to ounces, it would round to 4.
The answer depends on the units used for the given quantity. It should be plainly obvious to anybody that the answer for 3.50 grams will be very different from that for 3.50 pounds. So, without any information about the units for the given quantity, it is not possible to give a sensible answer.
What is 3.81 rounded to the nearest ounce?
5
Gg
3
350
345 rounded to the nearest 10 is 350
3.5 oz.
350
350
350
650
350
30
11
8.2
It is: 350 rounded to the nearest ten