We do not know that it is correct that Shaykh-Al-Islaam Ibn Taymiyyah used the supplication attributed to him when finishing the Qur’aan. We have not found anything mentioned about it in his Tafsir.
However, it is popularly attributed to him, and we don’t feel that there is anything wrong with it. If people say other supplications, then that is acceptable as well, because of the absence of any evidence to specify a particular supplication.
With Allaah is the facilitation to do what is right. May Allaah send peace and blessings upon Muhammad, his family, and his Companions.