A new lawn irrigation system for your home (or another building structure or property) would not actually be a purchase (or cost) eligible for a sales tax deduction.
Instead, such an expenditure is considered a property "improvement," and so it goes toward increasing the cost basis in that property. This becomes relevant when you sell your home, or other property, in that there is less of a (potential) capital gain.
A quick example will help illustrate that. Let's say that I purchase a building and pay $400,000 for it. Several years later I sell the building for $600,000. My gain is $200,000. But if I've made "improvements" to the property in the meantime, like adding a new roof, or installing a lawn irrigation system at a cost of $10,000, then my "basis" in the property is now $410,000. My gain, upon sale, is figured at $190,000, instead of $200,000, because my basis has been improved by $10,000.
Although simplified, this example does show what an increase in cost basis basically means.
For more details on this, and to verify that what is explained here is in fact correct, you may wish to look to IRS Publication 523, Page 12, where you will see "lawn sprinkler system" explicitly mentioned by the IRS as an item that increases cost basis in real property. Here is a courtesy link to that document:
https://www.irs.gov/pub/irs-pdf/p523.pdf
Thank you for asking this important question.
