C++: Calculations are incorrect when entering a certain input - c++

Question

I've been teaching myself C++ on and off for a few months and now I'm trying to make a payroll system. Here's my code:
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
void wageCompute (int, int);
int main()
{
int loopTimes=0;
int empNum=100, workHours, otHours, rate, bPay, otPay, grossPay;
string empName, empPos;
cout << "PAYROLL FOR THE MONTH OF MARCH" << endl;
cout << "Employees: " << empNum << endl;
while (empNum>loopTimes)
{
cout << "NAME: ";
cin.ignore();
getline (cin, empName);
cout << "\nPOSITION: ";
getline (cin, empPos);
cout << "\nHOURS WORKED: ";
cin >> workHours;
cout << "\nWAGE PER HOUR: ";
cin >> rate;
bPay = workHours*rate;
cout << "YOUR BASE PAY IS: " << bPay << endl << endl;
cout << "HOURS WORKED OVERTIME: ";
cin >> otHours;
otPay = (1.5*rate)*otHours;
cout << "\nOVERTIME PAY: " << otPay << endl;
grossPay = bPay + otPay;
cout << "GROSS PAY: " << grossPay << endl;
wageCompute(bPay, grossPay);
loopTimes++;
}
return EXIT_SUCCESS;
}
void wageCompute(int bPay, int grossPay)
{
double rate, dedInsurance, dedMedical, totDeduct, netPay, tax;
if (bPay<10001)
{
rate = 0.05;
}
else if (bPay<15001)
{
rate = 0.1;
}
else if (bPay<20001)
{
rate = 0.15;
}
else
{
rate = .2;
}
tax = bPay*rate;
dedInsurance = bPay*0.05;
dedMedical = bPay*0.01;
totDeduct = tax + dedInsurance + dedMedical;
cout << "TAX: " << tax << endl;
cout << "SSS DEDUCTION: " << dedInsurance << endl;
cout << "Medicare DEDUCTION: " << dedMedical << endl;
cout << "TOTAL DEDUCTIONS: " << totDeduct << endl;
netPay = grossPay - totDeduct;
cout << "NET PAY: " << netPay << endl;
}
The part where it goes wrong is when I input a certain value for the Hours Worked, Wage per Hour and Hours worked overtime. The program checks the basic pay for the suitable amount of tax it should deduct, what I input was 160 for the hours worked, 100 for the wage per hour, and 10 for overtime. I've tried lessening and increasing it and it worked just fine it seems that it's just these combination of numbers is the part where it goes wrong.
A screenshot of the output:

Answer 1

Your question isn't very clear but I suspect that what you are seeing here is a well known limitation of floating point numbers; numbers that are easy to represent exactly in base 10 don't have an exact representation in base 2. One example : 0.1 in base 10 is 0.0001100110011… repeating in base 2; the accuracy of the approximation depends on how many bits one is willing to use to write it.
An alternative approach is to use integer arithmetic with a known precision, so say you want to calculate to the nearest hundredth of a penny (I'm using UK currency here). Represent £1.01 as 10100 and when your finished val / 10000 is the pounds and (val % 10000) / 100 is the pence. If needed you can implement some more complex rules around rounding for the pence.