Hi rioerdana,
They still sell the five inch mattress on Amazon here but it’s fulfilled by Amazon and isn’t sold directly by Tuft & Needle so your purchase would be subject to the 30 day Amazon large item return policy and the return costs involved (see post #11 here) instead of the Tuft & Needle 100 day free return policy and you wouldn’t be eligible for the TMU discount.
Outside of a mattress for a guest bedroom or a child though … I think that the 10" would probably be a better choice for most people.
Either way though … congratulations on your new mattress 
Phoenix