Charm prices like 9.99 can boost initial conversions because they feel cheaper and trigger impulse buys. But round prices, like 10.00, often build more trust and reduce perceived manipulation, which can increase repeat visits and long-term loyalty. Over time, that loyalty can outweigh small gains in conversion rate. The best choice depends on product type and audience sensitivity. For low-consideration purchases, charm pricing may perform better. For premium or subscription-like experiences, round pricing can strengthen brand perception and lifetime value.