Leeds (24) 54
Tries: Gibson, Burrow, Smith, Ablett, Lauitiiti,
Tansey 3, Webb, McGuire Goals: Sinfield (6), Ellis
Castleford (6) 12
Tries: Owen, Dorn Goals: Dixon (2)
Jordan Tansey grabbed a hat-trick as reigning champions Leeds clinched a top-two finish with a 10-try rout of bottom club Castleford.
Ashley Gibson scored an early try and was followed by Rob Burrow, Lee Smith, while Ali Lauitiiti proved unstoppable on a 10-metre run to the line.
Tansey registered try number six before Brent Webb scored the night's best try.
Ryan McGoldrick and Luke Dorn replied for Castleford but Leeds' Danny McGuire and Burrow executed superb touchdowns.
The outclassed Tigers look certain to collect the wooden spoon after conceding a half-century of points for the fifth time this year.
And the visitors, who were led out by Craig Huby on his 100th appearance, were dealt a blow before kick-off when experienced scrum-half Brent Sherwin pulled out with a foot injury.
The visitors managed to put the champions under pressure and were rewarded on 20 minutes when right winger Richard Owen took Dorn's long pass to cross at the corner and Kirk Dixon added the touchline conversion.
But the Rhinos unsurprisingly began to assert themselves, and their lead at half-time would have been even more emphatic had Sinfield succeeded with more than two of his five conversion attempts.
Castleford rallied and pulled a try back through stand-off McGoldrick after 65 minutes but Leeds finished strongly.
In-form Burrow scooted clear to send McGuire over and then slick passing enabled Tansey to score his second try, with Sinfield taking his goal tally to six.
Tansey then sprinted 80 minutes for an interception try to complete his hat-trick and Ellis fittingly rounded off the scoring with the goal.
Leeds coach Brian McClennan:
"There was a bit of a flat period in the third quarter, other than that I was pretty pleased with the players.
"The discipline was good. The boys were getting very frustrated out there.
"There were hands on the ball, the 10 metres was non-existent at times and it was hard to get any momentum.
"We weren't really thinking about the league positions. It was at the back of our mind. We just wanted to perform well.
"We're getting confidence yet we know there is a whole lot more in us."
Castleford coach Terry Matterson:
"We really didn't get a chance - Leeds don't need a hand. You saw the kind of tries they score when they get the opportunity.
"I didn't think we did much wrong at 10-0 down but I was very disappointed with the second half."
Leeds: Webb, Smith, Ablett, Senior, Gibson, McGuire, Burrow, Leuluai, Diskin, Peacock, Ellis, Kirke, Sinfield.
Replacements: Lauitiiti, Scruton, Burgess, Tansey.
Castleford: Donlan, Owen, Shenton, Dixon, Wainwright, McGoldrick, Dorn, Higgins, Moore, Huby, Guttenbeil, Lupton, Westerman.
Replacements: Leafa, Henderson, Catic, Sargent.
Referee: T Alibert (RFL)