Rounding Something's Cost

function ceiling(n, s = 1000) {
    var ratusan = n % 1000;
    var pembulatanRatusan = Math.ceil(ratusan / s) * s;
    var ribuan = n - ratusan;
    return ratusan <= 500 ? ribuan : ribuan + pembulatanRatusan;
}

console.log(ceiling(12600, 1000));