C++ :: Rounding And Converting To Integer?

Ok so I'm in a programming 1 class working with c++. I have the following assignment:

Write a C++ program that:
asks for and accepts the Percentage earned with as a double (i.e. 75.45)
rounds it to an integer (>= .5 rounds up, <.5 rounds down.)
prints the original Percentage and the corresponding Grade and Points exactly as shown below.
prints an error message for any input that is less than 0 or greater than 100.

For example, if user enters 89.4, the program prints out:
Percentage: 89.4% Grade: B Points: 3.00
You must use an if-else statement to do this in your program.
Use fixed and precision output manipulators (see Ch. 3) to display the values with the exact precision shown above.

IMPORTANT:
Each if statement condition should contain only one comparison! read this again
This means code that is similar to this is NOT okay:  if (Percentage >= 80.00 && Percentage <90.00)
This code is not acceptable because the if statement condition above has two comparisons.
(Hint: If you order your if-else chain statements correctly, you will only need one comparison in each.)

I have the program working, but I'm pretty sure I'm not rounding how my professor would like it to. This is my code:

#include <iostream>
#include <cmath>
#include <iomanip>

[Code].....

So my issue here is the rounding, and then theres the converting the double percetnage to an integer. In my next assignment I have to write the program with a switch statement.