Add line or field for Tips/Gratuity

The scan receipt works great for restaurant receipts, but it only captures the printed values and forces me to edit in order to add the tip. Can you add a tip line item. Would be nice to see in reports later too.
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You can also write off tips to cabbies, valets, maids and other non-meal related people as travel expenses. Keeping track of these values is important.
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Ideally:
Make the "Total" field calculated as the sum of "Purchase", "Tax", and "Tip" -- rather than direct entry.

Track total tip amount in report summary