Yes, I can definitely help you with that! Here's how you can round your prices to end in .99 after increasing them by 5%:

1. Start by multiplying your original price by 1.05 to increase it by 5%. For example, if your original price is $15.00, you would multiply it by 1.05 to get $15.75.
2. Next, subtract the remainder when you divide the result from step 1 by 1. This will give you a number that ends in .xx. For example, if your result from step 1 is $15.75, you would subtract 0.75 to get $15.00.
3. Finally, add 0.99 to the result from step 2 to get your final rounded price that ends in .99. For example, if your result from step 2 is $15.00, you would add 0.99 to get $15.99.

So in summary, to round your price to end in .99 after increasing it by 5%, you would multiply your original price by 1.05, subtract the remainder when you divide the result by 1, and then add 0.99 to the result. I hope that helps!