The rogue has the [Uncanny Dodge](https://www.dndbeyond.com/characters/classes/rogue#UncannyDodge) class feature, which says this (PHB, pg. 96):

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> Starting at 5th level, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.
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As pointed out in the answers to [this question](https://rpg.stackexchange.com/questions/102091/can-you-use-uncanny-dodge-against-extra-damage-effects), if an attack has multiple damage types, you half all of it. So consider the ***Spiked Bone Club*** attack of the [Grimlock](https://www.dndbeyond.com/monsters/grimlock) (MM, pg. 175):

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> ***Spiked Bone Club***. *Melee Weapon Attack:* +5 to hit, reach 5 ft., one target. *Hit:* 5 (1d4 + 3) bludgeoning damage plus 2 (1d4) piercing damage.
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The Grimlock attacks the level 5 rogue and hits, and the DM rolls damage. The first d4 gives a 2, giving a total of 5 bludgeoning damage, and the other d4 gives a 3, giving a total of 3 piercing damage. The grand total is 8 damage.

[Given that damage is rounded down when halved](https://rpg.stackexchange.com/a/59009/35259), do we:

* round each individual total down, which in this example is (5 / 2) + (3 / 2) = 2 + 1 = 3?
* round down the grand total, which in this example is (5 + 3) / 2 = 8 / 2 = 4?