All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
In general, according to the most preponderant opinion of the scholars a dead person benefits from the reward of good deeds that a live person performs on his behalf [on behalf of the dead]. However, if one does so at a particular time, in a particular method and repeats that a specific number of times, then this is not reported in Sharee'ah (Islamic Law) and this is included in what some scholars call additional innovations.
The same thing applies to reciting Chapter Yaseen [Quran 36] a particular number of times in Tahajjud prayer so that the supplication would be accepted.
In any case, a Muslim is permitted to seek approach of Allaah in his supplication through a good deed that he did, and he may also seek approach of Allaah through Allaah's Names and Attributes, and then exalt the mention of the Prophet .
Allaah Knows best.