There is deity associated with each tithi. It will be a good practice to propitiate the tithi devata while performing rituals.
Pratipada - Krupeetayoni (Agni)
2 - Brahma
3 - Sankara
4 - Ganapati
5 - Dantashooka
6 - Kartikeya
7 - Martanda (Surya)
8 - Mahesvara (Siva)
9 - Durga
10 - Dandadhara (Yama)
11 - Visvedevah
12 - Madhava
13 - Pushpeshu (Kama)
14 - Parvateenadha (Siva)
15 - Chandra