Mod值下降1

Question

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>

int main(void)
{   
int loonies, quarters ;
double amountdue, balanceowing, owing;

printf("Please enter the amount to be paid: $");
scanf("%lf", &amountdue);

loonies = amountdue / 1;
balanceowing = (amountdue - (int)amountdue);

quarters = (balanceowing / 0.25);
owing = ((int)(balanceowing*100) % 25);



printf("Loonies required: %d, balance owing $%.2lf\n", loonies, balanceowing);
printf("Quarters required: %d, balance owing $%.2lf", quarters , owing/100);
return 0;

}

我要输入值8.68并获取输出

Please enter the amount to be paid: $8.68  
Loonies required: 8, balance owing $0.68  
Quarters required: 2, balance owing $0.18  

这是我通过解决方案得到的输出

Please enter the amount to be paid: $8.68  

Loonies required: 8, balance owing $0.68  
Quarters required: 2, balance owing $0.17  

为什么欠值返回的值= 0.17？ 68 mod 25 = 18

这是四舍五入吗？