This is a very big reason the notion that one builds an entire page in Photoshop, gets approval of the image, then the page is reconstructed in HTML/CSS is a pretty poor workflow in modern times.
It is rare that HTML type and placement will always match a Photoshop document. This in addition to someone creating a full page .psd file with no understanding of how CSS/HTML works can lead to issues. Anyone familiar with CSS wouldn't be setting every line of type to a different size. (Unless it's clearly intentional such as headlines, sub-headlines, then body text)
In general, there needs to be some "wiggle room" between a flat image representation of a page and a live HTML/CSS page. Trying to be exact can be a lesson in frustration.
I would use my best judgement to convey the intent of the type, not worry about exact point sizes. If the bulk of body text is set at 14pt/px, and there are a few occasional lines set at 12pt/px or 15 pt/px, then I'd use 14px as the size. Unless, there is some purposeful intent to the varied type sizes. I wouldn't make 24, 14, 18, and 30pt type all the same size. But 12, 13, 14, and 15pt could probably all be unified.
This can, of course, cause the "that doesn't look like the image I approved" statements from clients.. in which case.. see the first paragraph here.
