I'm just beginning at C, so I have a few questions on something. I'm trying to get user input and multiply it by tax rates. The scanf function is not working for me. It doesn't read anything into my variable and then it prematurely exits.

Code:
#include <stdio.h> //include library stdio


//main method
void main()
{
     /***********************
      *  Del Mar - 7.25%    *
      *  Encinitas - 7.5%   *
      *  La Jolla - 7.75%   *
      ***********************/
      
     //print out the 'menu' of tax rates
     printf("*** Tax Rates ***\n");
     printf("-----------------\n");
     printf("Del Mar - 7.25%\n");
     printf("Encinitas - 7.5%\n");
     printf("Del Mar - 7.75%\n\n\n");
     
     
     
     
     
     
     
     double new_amount = 0;
     printf("Current amount = $125\n\n");
     printf("Enter an amount: ");
     scanf ("%d", &new_amount);
     
     new_amount += 125;
     double tax_rate = .0725;
     double tax_total = tax_rate*new_amount;
     double total_amount = tax_total+new_amount;
     
     printf("$%d at Encinitas tax rate:\n",new_amount);
     printf("-- Tax:    %f\n", tax_total);
     printf("-- Total:  %f\n", total_amount);


     getchar();
     
}

Why is it always giving me 0 as the new amount no matter what I input?

Also, is there some way to add some simple error checking, like making sure the user enters a number? If so, could you point me to a tutorial or something?