Round CC surcharge immediately after calculating for event-based payments

[wdst-gcet]

Issue

Accounts with a credit card and auto-billing enabled would occasionally show a balance of 1 cent when a credit card surcharge percentage was applied during the nightly cron job. However, this issue did not occur when billed manually.

Cause

The issue arises in edge cases where small rounding variations accumulate, leading to a 1-cent difference for some transactions.

Scenario 1: $85.00 with a 2.3% surcharge

1. Surcharge calculation: $85.00 × 2.3% = $1.955
2. Adding the surcharge: $85.00 + $1.955 = $86.955
3. Rounded total: $86.96

Now, if the system later recalculates the total without first rounding the surcharge, it might continue using the unrounded surcharge value ($1.955). This can cause minor rounding discrepancies at certain steps, potentially leading to a missing cent.

Scenario 2: $155.07 with a 2.3% surcharge

1. Surcharge calculation: $155.07 × 2.3% = $3.56661
2. Adding the surcharge: $155.07 + $3.56661 = $158.63661
3. Rounded total: $158.64

In this case, despite the surcharge having multiple decimal places, when it is added and rounded, the final total remains accurate. The rounding difference is too small to cause a discrepancy, meaning the total aligns correctly.

Fix

The fix ensures that the surcharge is rounded to two decimal places immediately after calculation, preventing rounding errors and ensuring the total remains accurate to the nearest cent, preventing rounding discrepancies

…hopefully, this doesn’t introduce any new issues.

[wdst-gcet]

After waiting for a full billing cycle I think this fix is good.