There are 3 syllables in NITTO but not in the way you think - the 'tt' doesn't really denote a syllable, just a pause. Before I get to that, let's look at the 3 ways of writing NITTO in Japanese:

1.
日東 (literally SUN & EAST)
These are the Chinese characters, as used on the Japanese language NITTO website.

2.
にっとう - in 'hiragana', a syllabary commonly used when writing for children who have yet to learn the more complicated Chinese characters. It's also used for what are called 'particles', such as 'ga', to denote the subject or object of a verb, for prepositions and for verb endings.

3.
ニットウ - in 'katakana', commonly used for foreign loanwords, or for Japanese words to give them emphasis. NITTO is often written this way.


And the word NITTO itself:

ニ/ni - the 1st syllable, pronounced 'knee'

ッ - not a syllable but denotes what is called a glottal stop, like when we say 'hot tea'. We form the t but stop short of pronouncing it, stopping it in the glottis instead before continuing with the t of tea. We do the same thing with the p of stop in 'stop short'. (FWIW, the staccato sound of Cantonese speakers speaking English is due to the fact that Cantonese has the most glottal stops of any language in the world.)

ト/to - the 2nd syllable, pronounced a bit like toe (as pronounced by a Spanish speaker of English) or a bit like the to/ of top in British English.

ウ/o - the 3rd syllable, which continues the o of 'to', effectively doubling the length of to. (A confusing aspect of ウ is that it's pronounced the same as the oo of who except when used to lengthen the vowel sound of o.)

NI, TO & O all have equal length.

So I guess the best way to write NITTO in such a way as to elicit the closest pronunciation of the original Japanese among English-speakers is NEAT TOE.