As the other answers have noted, Rand does not use much taste or smell imagery in this novel. Like most authors in our primarily visual culture, she relies on images we can see in our mind's eye. In addition, however, to the scent imagery others have noted, Rand includes imagery that, while primarily visual, performs double duty, which is often how imagery operates. When Equality 7-2521 and the Golden One sleep in the forest after they escape, Equality notes that

The fires smoulder as a crown of jewels around us, and smoke stands still in the air.

This is primarily a visual image, but at the same time we can imagine the smell of the fire and smoke as Equality and the Golden One must have experienced it.

As for taste imagery, we learn that in their dystopic world. Equality and the Golden One eat a mid-day meal and a dinner, but we learn nothing of what is served or what it tastes like, attesting to the dullness of that society. However, when out in the woods, the two kill and eat a bird:

we cooked the bird, and we ate it, and no meal had ever tasted better to us.

We learn nothing about the actual taste of the bird or even what kind of bird it was, but do learn that it tastes very good to them, in part because they caught it themselves. When they find the house and the cook pot, they kill a goat to eat:

We killed a mountain goat, and we brought its flesh to be cooked in a strange copper pot we found in a place of wonders, which must have been the cooking room of the house.

Again, Equality offers no particular taste or scent images, but we can imagine the taste and smell of roasted meat.

We made a fire, we cooked the bird, and we ate it, and no meal had ever tasted better to us. And we thought suddenly that there was a great satisfaction to be found in the food which we need and obtain by our own hand. And we wished to be hungry again and soon, that we might know again this strange new pride in eating (from part Eight: It has been a day of wonder, this, our first day in the forest).

The above is an example of gustatory (taste) imagery. Here, Equality 7-2521 kills a bird, cooks it himself, and eats it. It's his first kill in the forbidden forest, and he finds that he enjoys this transcending experience of autonomy and independence. The food tastes better than anything he's been forced to eat for most of his life. The imagery illustrates Equality 7-2521's wonder and delight in being able to savor the taste of roasted bird meat.

 We feel it also, when we are in the Home of the Street Sweepers. But here, in our tunnel, we feel it no longer. The air is pure under the ground. There is no odor of men. And these three hours give us strength for our hours above the ground (from Part Two: Liberty Five-Three Thousand).

The above is an example of olfactory (smell) imagery. Here, Equality 7-2521 revels in being alone in the tunnel he has discovered. The air is clean in the tunnel, and he tells us that, in his opinion, "there is no odor of men" to mar the immaculate purity of the place. The imagery illustrates how special this tunnel is to Equality 7-2521; it smells clean and is a cocoon of peace to him.