When you are calculating the average of the number of people who do something, and you get a value with decimal points, should I still round up when the decimal point is > or = 5, and round down when it's < 5?
e.g. if I get an average of 4.3, should I round up or down?
And if I get an average of 4.7, should I round up or down?
There is no intrinsic reason to round at all. Even though all your samples have a whole number of people the mean may well not. Just report $4.3$ or $4.7$ or whatever you get.
If you are going to round it, the usual rounding rules apply, so $4.3$ would round to $4$ and $4.7$ would round to $5$ if you wanted a whole number.