Problem 6 How to round correctly

Hello i am trying to solve the problem but there are some cases where the program works and others dont. Can someone help me??? Some of the numbers round and others dont

#include <stdio.h>

int main(void)
{
    int size;
    int i = 0;
    float f = 0.0;
    int pro = 0;
    scanf("%d", &size);

    int res[size];
    int arr1[size];
    int arr2[size];


    for (i = 0; i < size; i++)
    {
        scanf("%d ", &arr1[i]);
        scanf("%d ", &arr2[i]);
    }

    for (i = 0; i < size; i++)
    {
        f = arr1[i] / arr2[i];
        pro = f;
        f - pro;
        f * 10;

        if (f >= 5)
        {
            f + 1;
        }

        res[i] = f;

        printf("\n %d \n", res[i]);
    }


    return 0;
}