I've tried to figure this one out by referring to the MySQL manual, but can't. If you can help with this, I would appreciate it.

Here is the query in natural language, to help avoid confusion of my intent.

In xcart_products.list_price, if the two digits to the right of the decimal point equal to 00, 95, 99 or 50, then take no action, else change the first digit to the left of the decimal point to 5 and the two digits to the right of the decimal point to 00.
For example, if xcart_products.list_price = 132.99, then no change. If it = 132.92, then change to 135.00.

Thank you!