Weekly bookings

I am creating a mock up site for a Retreat Center website. They don’t offer nightly bookings, their customers are generally church groups and they only book by the week during the summer months.

I can easily set the min 7 days requirement but the pricing is where I get messed up. Their cottages don’t have a nightly rate and since $1100 a week or $850 a week doesn’t easily divide into 7 nights I can’t create a clean $1100 booking, at best I get $1099.98 which isn’t making the customer happy.

Is there any way to create a flat rate for weekly bookings?