Hey @david-kaplan .
Thanks for reaching out.
Since the Shopify platform does not directly support rounding to the nearest 0.05 or 0.00. The discount can be a percentage or a fixed amount off the original prices. However, the final price after the discount applied may not necessarily end in 0.05 or 0.00. With that being said, there are third-party applications available in the Shopify App Store that help with price rounding.
I did compile a list of third-party applications that you may be interested in using, I would suggest taking a look through the list to see if one may catch your interest:
Let us know if you have any questions.