Rounding float number to 1 decimal point in stored procedure

In this stored procedure, I get an output for "retention" that look like this:

58.82352941177

When I want it to look like this:

58.8

How can I get it to round the number to one decimal point?

Here's the SP:

Alter Procedure SP_RETENTION_PER_STUDIO_PER_MONTH  (@Studio_ID int)
as
select
StudioID=isnull(a.StudioID,d.StudioID)
, "month" =isnull(a."month" ,d."month")
, "year" =isnull(a."year" ,d."year")
, retention=convert(float,isnull(a.Payments,0))/(isnull(a.Payments,0)+isnull(d.Deacs,0))*100.0
from
(
select StudioID, "Month"=Month(date), "Year"=Year("date"), Payments=count(*)
from fasterfitness.Payments
where NewRenewal = 'Renewal'
group by StudioID, Year(date), Month(date)
) a
full join
(
select StudioID, "Month"=Month(DayDeactivated), "Year"=Year(DayDeactivated), Deacs=count(*)
from fasterfitness.Deactivations
group by StudioID, Year(DayDeactivated), Month(DayDeactivated)
) d on a.StudioID=d.StudioID and a."Year"=d."Year" and a."Month"=d."Month"
WHERE a.StudioID=@Studio_ID
order by StudioID, "Year" DESC, "Month" DESC