The Welsh, beaten 25-21 by champions England last weekend, will finish second in the standings while Italy come bottom after losing all five matches.
“We are still disappointed with last week and we owed it to the fans,” Wales captain Dan Lydiate told the BBC.
“We still gave away some soft tries but the boys played their hearts out and I couldn't ask for anything else from them,” added the flanker who was leading the side in place of the injured Sam Warburton.
“Two bad halves of rugby let us down in this championship and let's hope we learn from that and we never start again like we did in the game against England.”
Scrumhalf Rhys Webb barrelled over from close range to open the scoring for the hosts, celebrating his first start since sustaining a serious leg injury before last year's World Cup.
Italy scrumhalf Guglielmo Palazzani was sin-binned for falling offside and flyhalf Dan Biggar crossed for the second Welsh try before centre Jonathan Davies finished off a flowing move under the posts to stretch the lead to 27-0 at halftime.
Centre Jamie Roberts, winger George North and fullback Liam Williams touched down as Wales cut loose in the second half and replacement flanker Ross Moriarty added two late scores before Gareth Davies completed the rout.
Palazzani and centre Gonzalo Garcia grabbed Italy's consolation tries.
“We lost against a great team in Wales which shows the young guys must work on this defeat and get better for future,” Italy captain Sergio Parisse said.
“The campaign was really difficult, every team gets injuries but for us it is maybe much more difficult because we don't have the depth but no excuses, from June we have another staff and maybe things will change.” – Reuters
Original source: Wales demolish Italy