invoice_lines.price is stored as a float.

Traditionally, integers with a magnitude of up to 24 bits are exactly representable (<= 16,777,216). So theoretically, a value like 11,111.11 is representable to within half a cent (and should render correctly). Instead, when we create an invoice with a single line we observe the following:

• $11,111.11 -> $11,111.10
• $111,111.1 -> $111,111.0
• $1,111,111 -> $1,111,110

This is because rather than directly output the stored float value, MySQL rounds it to 6 decimal sigfigs. https://bugs.mysql.com/bug.php?id=87794

Since it is still stored exact, casting to another type will change any past invoices. Past lines need to be rounded to 6 sigfigs at rest to maintain records.