The Orc who knew too much

[Findegil]

I agree to most of what Mithadan told, but I think that Grishnakh is not under the order of a or the Nazgûl (or not more than a lower rank officer would be to a general of another department of an army). Considering what would happen if he got hold of the Ring, it is much more likely that he is trusted by Sauron himself.
An orc-comander as smart as Grishnakh using the Ring would be a danger for the Nazûgl themself: He could - in a way - comand them.

In contrast we might understand Grishnakh's "trusted messanger" as trsuted by Sauron himself: We have learned that for the Nazgûl there was no doubt who was the Master of the Ring - even so they were mighty among the servants of Sauron, they could not withheld the Ring from him, if they got hold of it - or at least that was the believe of our narrartors (real or feigned) and Sauron himself. With the Nazgûl the obivous reason is that Sauron held the Nine to which the Nazgûl were slaves fare more direct then to the One. But if Sauron could bring other underlings to the same beleive that the One would not help them in a rebellion against him, they would be really trustworthy messangers. And the behavior of 'the West' would give more credit to such a believe: Why in the view point of an Orc shouldn't the Wiese us the One, if it would help them against Sauron? So for Grishnakh it might seem that only Sauron could make any use of the One Ring and that his best option would be to deliver it to him and profit from his 'thankfullness'. And as with every good lie their is a spark of truth at its core: As we read in the letter with the alternative endings, the full potential of the One Ring could really only be used by Sauron or a very might opponent that was or became as corrupted as Sauron himself.

Respectfuly
Findegil