This depends on the meaning of "can be said to rhyme". Judgments about the acceptability of rhyming really only make sense in a particular artistic context. I'm using classical Chinese poetry and modern Mandarin pop songs as examples.
Classical Chinese Poetry
The rules about rhyming in classical Chinese poetry are complicated. Syllables which rhymed in Middle-Chinese often don't in Mandarin (and vice versa); in order to even assess whether a poem rhymes properly, you need to look up all the characters' Middle-Chinese tones and so forth. Also, since this style of poetry was being written well after the vernacular pronunciation had changed substantially, the writers had to look this stuff up in order to write poems that rhymed.
[Of the 13-yuán rime] As a so-called 险韵 “treacherous rime,” it was often assigned as the required rhyme on official poetry examinations, so that nervous candidates would mistakenly include words in an3b in the rhyme scheme. Or they might include words in an3a in a poem whose rhyme scheme was limited to an3b and an4. In either case, they would be considered to have 出韵 “left the rhyme-scheme”.
... In late Manchu times, 王闓運 (1833-1916) wrote a poem teasing his colleague 高心夔 (1835-1883), who twice received low scores on the official exams when the appearance of 13-yuán caused him to “leave the rhyme-scheme.” Wáng wrote:
[Two fourth-place finishes in one lifetime — to hell with 13-yuán!]
For a more complete exposition of this, read page 29 to 53 of this.
Mandarin Pop Songs
Pop songs rhyme. Mostly. Except when they don't. It's pretty much the same as in English pop songs. I did manage to find a couple of approximate rhymes:
zhuan3 yan3 guo4 qu4 duo1 nian2 shi4 jian1 duo1 shao3 li2 he2 bei1 huan1
ceng2 jing1 zhi4 zai4 si4 fang1 shao4 nian2 xian4 mu4 nan2 fei1 de yan4
ge4 zi4 ben1 qian2 cheng2 de shen1 ying3 cong1 cong1 jian4 xing2 jian4 yuan3
wei4 lai2 zai4 na3 li3 ping2 fan2 a shui2 gei3 wo3 da2 an4
Note, that despite the pinyin, huan and yuan do not have the same vowel. Also, yan and an don't either.