The use of rhyme and repetition in "The Raven", by Edgar Allan Poe, are meant to affect the reader in the following way:
It causes the reader to sense how desperate and devastated the speaker is.
Since the raven is a symbol of death and loneliness, as well as of a somber state of mind, the speaker wants it to leave his house. The presence of the animal affects the speaker in an unbearable way, since it reminds him of the loss of his significant other.
The rhymes make it for a feeling of frantic desperation, whereas the repetition, particularly "nothing more" and "nevermore", shows how strongly mourning affects the speaker, how devastated he is.
We can see how badly the speaker wants the bird to leave in the following passage:
"Take thy beak from out my heart, and take thy form from off my
door!"
Quoth the Raven, "Nevermore."
