While geotargeting countries by IP is easy and the accuracy rates are above 99.8%, when we talk about cities the accuracy depends on the city and database used.
WordPress Geotargeting Plugin uses Maxmind GeoLite free databases to query countries and cities which is not as accurate as their premium databases like the GeoIP2 City or GeoIP2 City Insights (for USA)
We support .mmdb database format, so if you want to purchase their premium databases, you can simple drop and replace the geotargeting-pro/includes/data/GeoLite2-City.mmdb file and you will benefit of more accuracy rates.
If you instead purchased GeoIP2 City precision just paste your user ID and license key in the settings page of the plugin and choose which service you purchased( city , country or insights )
To check a rate comparison between countries, cities and database please check the geotargeting accuracy chart.