Spelling rhyme is a loose term for words that look as if they should rhyme because they share a similar spelling, but do not actually rhyme when spoken. The more common poetic term is eye rhyme or sight rhyme. Poets may use this kind of near-match to create visual pattern on the page without matching final sounds.
Example
The light was caught in the bough of the tree,
though the night had turned cold as could be.
Here, bough and though look related on the page, but they do not rhyme in speech.