The verb is conjugated based on the subject, not the object, since Raj is a singular man, everything will be conjugated as such, no matter if what he's selling is masculine, feminine, or plural, it will always be बेचता.
The exception is that transitive verbs do agree with their objects in the preterite tense and perfect aspects becaues of ergative alignment. "Raj sold apples" would be राज ने सेब बेचे, with बेचे agreeing with सेब.