How to print previous multiple of 10 , this program prints next multiple of 10

Define a method which returns the sum of three rounded numbers. If the right most digit of the number is lessthan 5, then round off it's value to the previous multiple of 10 otherwise if the right most digit of the number is greater or equal to 5, then round off to the next multiple of 10.

public class Roundofff {
public static void main(String[] args) {
		        int a = 23, b = 34, c = 69;
		        System.out.println(sumOfMultiples(a, b, c));
		    }

		    public static int sumOfMultiples(int a, int b, int c) {
		    	if(a <= 0 && b <= 0 && c <= 0){
		    		return -1;
		    	}
		    	a = a + (10 - a % 10);
		    	b= b + (10 - b % 10);
		    	c= c + (10 - c % 10);
		    	
		    return a + b +c;
		}
}