I think you're close, but you're using the same gradinitial
value in every calculation, so your increase value is always the same.
<cfset loopterm = 360>
<cfset incr = .04975>
<cfset newamt = 274.22>
<cfloop from="1" to="#( loopterm / 24 )#" index="i">
<cfoutput>
#dollarformat(newamt)#<br />
</cfoutput>
<cfset newamt = newamt + ( newamt * incr ) />
</cfloop>
This produces a result set like this:
$274.22
$287.86
$302.18
$317.22
$333.00
$349.57
$366.96
$385.21
$404.38
$424.49
$445.61
$467.78
$491.05
$515.48
$541.13
It's not perfect, but hopefully that gets you on the right track.