It is more or less round. While modern milled coining created nice neatly rounded coins, throughout the history of hammered coins they were very rarely anything like a perfectly rounded coin. They were creating these things in a mass production environment where they made tens of thousands (or more the Romans), quality control was focused on weight over all else. For silver coins and gold some issuers did often try to hold to higher aesthetic standards, there's some Roman/Sassanian/etc coins that are fairly nicely rounded (though often still a bit ragged on the edges from being hammered) but for bronzes they did rarely focused on this (the Ptolemaics did, some others did, most didn't care).