If your business is located in an area that mandates Tax Inclusive Pricing, you can utilize Tax Inclusive Pricing by adjusting settings in Magento 2, POS, and the Upload tab of the Accumula Settings Pane.
First, be sure that your Tax Settings are set correctly in the Accumula Settings > Magento > Taxes tab:
When using Tax Inclusive Pricing the Tax Mode must be set to Match Tax Code Name. If you're using a POS that can have tax inclusive and tax exclusive pricing sources your Price Source should be set to one that is Tax Inclusive on the Upload Page:
Magento 2 Settings
In Magento 2, there are several tax settings that must be adjusted. Please consult your Magento Developer if you're not sure what to change.
Most of the settings you will need to change are located in Stores > Configuration > Sales > Tax.
See our Magento 2 - Match on Tax Code Name documentation for how to configure taxes to sync with POS.