class Order extends Eloquent {
    public function lineitem() {
            return $this->hasOne('AppModelsLineItem','id','lineitem_id');
    }
}
class LineItem extends Eloquent {
    public function totals() {
        return $this->hasMany("App\Models\LineItemTotal",'lineitem_id');
      }
}

Collection {#530 ▼
  #items: array:7 [▼
    0 => LineItemTotal {#506 ▶}
    1 => LineItemTotal {#531 ▶}
    2 => LineItemTotal {#522 ▶}
    3 => LineItemTotal {#508 ▶}
    4 => LineItemTotal {#509 ▶}
    5 => LineItemTotal {#510 ▶}
    6 => LineItemTotal {#511 ▶}
  ]
}

dd(isset($order->lineitem->totals));

false