Maximum Server Memory adjust in blocks of 1024MB?
It's reasonable to assume, although I have no way to know, that the difference between allocating 3000 MB and 3072 MB is just those 72 MB as memory allocation is much more granular than, say, 128 or 256 MB.

The minimum amount of memory allocated to each query is 1024 kB, configurable as low as 512 kB (source). A fair guess is that memory allocation units are anywhere between that of disk I/O operations (64 kB = 1 extent = 8 pages) and 512 kB.

Either way, 72 MB back or forth probably won't make any difference.