Sounds reasonable - I do similar. Two things about rounding:
(1) did you know that when you express an opinion of, let's say, $300,000 - you're actually expressing that opinion down to the penny? IOW - $300,000 is different than $299,999.99 and it's different than $300,000.01. In fact, the ONLY number that equals $300,000 is $300,000.00. So when you've rounded to the nearest $10k, $100k, or $1M - you're expressing an opinion of value down to the penny.
Now - no one would raise an eyebrow at someone expressing an opinion of $275,000, but they'd frown at someone willing to express an opinion of $276,105.95. Even though - in effect - you're doing the exact same thing. You're actually saying $275,000.00 (which is expressing the opinion down to the penny). Do you really think you're that good? Or to put it another way - do you really think your data is that good? Or to put it even another way: Why would $275,000 be more supportable than $275,001? Or $274,999? Or $274,999.99?
(2) when you round, you're actually expressing a range of value. If you round to the nearest ten thousand (let's say $280,000 for grins), you're actually saying that your opinion is between $275,000.01 and $284,999.99. So that, by admitting that you round, you're actually admitting that you express your opinion of value as a range.
To ZZG's point, I know this is higher order thinking - and may take a bit to sink in - but 'tis true whether you end up understanding the logic behind it or not.