This will depend on the site, branding, messaging, person's opinion, etc.
There are studies arguing for both, but you won't know the true answer for your site until you A/B test them.
My opinion: even numbers give a more premium / boutique feel, while decimal pricing gives a feeling of being on sale.
To get the best data, you'll want to try both.
On a basic level, with Shopify I like to test one variation for 24 hours, then the next variation for 24 hours, run it for a couple weeks (depending on traffic level), then compare the results of each. If you need help with A/B testing let me know.