c语言计算绝对值的题目中为什么输入99.99会输出99.98，输入9.9输出9.89

Question

#include<stdio.h>

int main(void)

{float a,b;

int c;

while(scanf("%f",&a)!=EOF)

{ b=(int)(a*100)/100.00;

    if(a>=0)printf("%.2f\n",b);

if(a<0)printf("%.2f\n",b*(-1));}

return 0;}