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.
Founder of
Speed Boostr (Shopify optimization experts, theme customization, custom app development).
Creator of
Shopify Analyzer (first performance analysis tool for Shopify sites, free for the Shopify community).
Creator of
Order Automator (auto tag orders and customers + auto fulfill orders + email notifications).
Creator of
Theme Scientist (A/B testing app) and
Tip Jar (add a tip button to your store).
