How do i reset the prices without sales prices?

Doesn't look like there is a setting for it. What is happening is when the plugin updates your price it is updating both the sale price and regular prices. This is also passed onto your customers, though while there seems to be no setting you can remove the sales badge from your theme easily depending on the theme.

For the general storefront theme this is the css to remove the sales badge.

ul.products li.product .onsale {
    display: none;