round just rounds the figure
1.8 = 2
1.5 = 2
1.4 = 1
3.25 = 3
etcetera
with multiplying I mean
round(3.25487) = 3
but
round(10*3.25487)/10= 3.3
this way you can work with decimals..
without using this there is no way to be sure the exact number you chose will be reached, for even with 0.0000001 difference the computer will not accept it
5.00000001 is not the same as 5 rounding the number will make it so..
there's also floor() always rounding down and ceil() always rounding up..