I got an excerpt from the Google Play Terms of Service:
"Taxes. You are responsible for any Taxes, and must pay for Content without any reduction for Taxes. If the seller of Content is obligated to collect or pay Taxes, the Taxes will be charged to you."Taxes" means any duties, customs fees, or taxes (other than income tax) associated with the sale of Content, including any related penalties or interest."
Purchases in Play Store are just like any other item sold locally: subject to 12% VAT (last time I checked). The prices you see there does not reflect the applicable VAT, as it varies depending on the country.
So in your case, if you purchase an item worth P135 and multiply it by 1.12, then you should have load of at least P151.20.
Hope this helps.