Going into day two of the LV= Insurance County Championship clash at Wantage Road, Northants lead by 108 runs with five wickets in hand.
Sanderson and Gareth Berg were the stars with the ball as Sussex were rushed out for just 106, taking five wickets apiece.
The south coast side actually recovered from at one point being 25 for seven, with Ollie Robinson's 49 not out at least seeing them reach three figures.
Northants lost openers Ben Curran and Ricardo Vasconcelos early to give the visitors hope.
But crucial partnerships between Rob Keogh (66) and Saif Zaib (66no), as well as Zaib and skipper Adam Rossington (27no) saw the County to 214 for eight at the close, and means they are in total conrol of proceedings.
“It was the perfect day, and we could have still been a few more runs ahead if we had caught all our catches," said Sanderson.
“That partnership between Rob and Saif has really set things up for us and put us in a strong position ahead of tomorrow.
“It was seaming about this morning but as the day went on it seemed to get better with the older ball and a bit of sun and wind."
Sanderson, who for the second game in a row took a wicket in the first over of the match, was delighted to at last get some serious reward for his bowling efforts, claiming his first five-wicket haul of the season.
“It has been frustrating so far this season beating the edge a lot but it all happens quickly when it starts," he said.
"It's the same with Bergy, who has bowled really well all season, so for him to get his just deserves with a five-for is just brilliant.
“It wasn’t feeling right in my action in the first couple of games but I worked on my action with Chris Liddle (bowling coach) and that has kick-started me to find my rhythm.
"Now I can bowl more overs and effectively, to find that click and rhythm will allow me to kick on.”