Paypal amount_x / amount precision issue - paypal

Question

I've encountered an issue with Paypal Standard integration that I don't really know how to approach. Let's say I've got a product that costs 0.019, of which I'm buying 100. For this situation, the form should look like:
<input type="hidden" name="amount" value="1.9">
<input type="hidden" name="amount_1" value="0.019">
<input type="hidden" name="quantity_1" value="100">
However, due to the Paypal double precision, the amount_1 field is incorrect.
I can do rounding, which will give me this:
<input type="hidden" name="amount" value="1.9">
<input type="hidden" name="amount_1" value="0.02">
<input type="hidden" name="quantity_1" value="100">
but this on the other hand will provide me with wrong total, of 2 (as the amount field will be ignored).
Is there any sensible way of handling this issue (apart for grouping the objects I'm selling)? I don't think I've seen any Paypal precision related questions :/
Edit: I can (and am) round the amount value, for the total of the order. I need however to display how many items the user buys.

Answer 1

When I was writing a store with 3 decimal places for pricing on large volume items (resistors, LEDs, diodes etc) we had to use line totals (and rounding) for dealing with PayPal.
Thus, our own internal system took care of volumes (as makes sense for order tracking, invoicing, packing, stock control etc) and PayPal just took the cash, whilst we could still track what was sold via PayPal if we had too (payment taken but error internally).
PayPal Example Invoice:
| Qty | Desc | Price | Line Total |
| 1 | Green LED 100 Units at $0.019 | $1.90 | $1.90 |
Large electronics distributor digikey.com uses this method.

Answer 2

Your issue is that you're not dealing with standard amounts. I don't believe I've ever seen anybody price something like you're showing here. You really have a price tag on an item of $0.019? That would be very confusing to buyers, I would think. You might simply consider adjusting your price so it follows standards.
Alternatively, you could go ahead and round like you said, which would give you the $2.00 total, but then you could add a 10¢ discount to get back to $1.90.