I see penalized rounding as the "same" kind (up for tonnage, down for damage).
Canon damage rounding is
very nearly always round up; basically the only thing I can think of that isn't is the AC 2 (which is, if one considers things, “actually” an AC 2.5)
Everything else rounds up.
In honesty a Light/Medium Blazer is effectively an Inner Sphere flavor heavy laser.
Edit: On a
completely different note, you might consider MMLs or modestly improved LRMs- the former were
canonically put together from spare parts in a Mechbay by a bunch of mercinary MechTechs, while the latter could really use the extraionus weight shaved off the larger racks (4t LRM 10, 6t LRM 15, 8t LRM 20) so it's no longer incentivised to mount stacks of LRM 5s if you're not putting Artemis on the things.
Similarly, MMLs with slightly better tube count would be great (even just going 9→ 10 on the largest size to keep the ×1.5-round-down theme going), or rounding
up for 5, 8, 12 (which makes them feel more “inner sphere ATMs”)