$scope.onUserAmountChange = function($summ) {
$scope.model.price = Math.round(($summ / $scope.model.amount_users), -1);
}
Math.round(785/10)*10
function round(n, f) {
f = Math.pow(10, -f);
return Math.round(n / f) * f;
}
round(785, -1) // 790