第1組我自己輸入答案輸出是對的貼上去卻差了0.01

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    double a;
    while(cin>>a)
    {
        if(a>=0.01&&a<=100)
        {
            a=a*9/10;
            a=a*100;
            a=floor(a);
            a=a*100;
            if(a!=100)
            a+=8;
        }
        else if(a>=100.01&&a<=500)
        {
            a=a*8/10;
            a=a*100;
            a=floor(a);
            a=a/100;
        }   
        else
        {
            a=a*6/10;
            a=a*100;
            a=floor(a);
            a=a/100;
        }
        printf("$%.2f\n",a);   
    }       
}