There is an obvious alternative here, which is to just absorb that fraction of cent, so the customer doesn't see it. Handling bug reports and infuriated clients costs more.
You could even just round up to the penny and ding the customer; if there is a 0.3 cent fraction coming from the payments gateway, turn it into a customer-facing penny, thereby collecting an extra 0.7 cents.
That way, too, there would almost certainly be zero complaints and bug reports.
If the customer is supposed to pay $103.45395 every month, you could turn it into $103.46, pocketing an extra $0.00605, or into $103.45, where you're out $0.00395.
Think about it; when you eat at a restaurant, often the prices for a meal are round like $11.50, even though the restaurants expenses are down to the penny. Why is that? Because they arbitrarily set the price. They don't say, oh, our ground beef supplier charges to the penny penny, so lunch will have to be $11.57.
Oh, the business teams found the approach puzzling---but what do they know, right? If they were smart, they would be software engineers.