Round number to nearest number ending in 2

int a=4999;// getting the user input
int b = a, c = a;// defining two variables 'b' is for finding nearest number bigger than user input and 'c' is for finding nearest number smaller than user input
int i, j;
// a for loop to finding nearest bigger number and keep it in 'b'
for (i = 0; ; i++)
  if (byte.Parse(b.ToString().Substring(b.ToString().Length - 1)) == 2)
      break;
  else
      b++;
// a for loop to finding nearest smaller number and keep it on 'c'
for (j = 0; ; j++)
  if (byte.Parse(c.ToString().Substring(c.ToString().Length - 1)) == 2)
      break;
  else
      c--;
//compare to nearest number that had been found and find wich one is more near to input number
if (i >= j)
  MessageBox.Show(c.ToString());
else
  MessageBox.Show(b.ToString());

int a=4999;
int c = a;
int j;
for (j = 0; ; j++)
    if (byte.Parse(c.ToString().Substring(c.ToString().Length - 1)) == 2)
        break;
    else
        c--;
MessageBox.Show( c.ToString());