Here is an example that you can modify to fit your exact data.
The sample data is in cells H4 to J6
The student number is in column H, the names are in column I and the results (not rounded) are in column J
H I J
4 1 maram 99.25
5 2 humar 99.75
6 3 doe 88.6
In Cell A1 enter the student number.
In cell A2 enter this formula: =VLOOKUP($A$1,$H$4:$J$6,2, FALSE)
In cell B2 enter this formula: =INT(VLOOKUP($A$1,$H$4:$J$6,3,FALSE))+IF(MOD(VLOOKUP($A$1,$H$4:$J$6,3),1)<0.25,0,IF(MOD(VLOOKUP($A$1,$H$4:$J$6,3),1)>=0.75,1,0.5))
The VLOOKUP function looks for the student ID in cell A1 in the first column of the data in $H$4:$J$6
In cell A2 it just returns the student's name from the second column (column I)
In cell B2, the rounding formula uses the students score in three places in the formula, so VLOOKUP is used three times to return the score from the third column (column J).
In the rounding part of the formula, I think that you should use >=0.75, for accuracy, rather than >=0.7, otherwise a score of X.7 will be rounded up, rather than returning X.5
As you enter different numbers in cell A1 you will get each students name and rounded results in A2 and B2.
Entering 3 in A1 gives the following:
2 doe 88.5