Two called Nightshade

Photos © Carol Tornow; © Gene Spesard

Douglas Nightshade has very tomato-like flowers with - you guessed it - 5 fused petals. Don't eat the fruits, though.

Photo credits: Flower, top fruit: © 2016 T. Beth Kinsey;
fruits: © 1966 - Present, Audrey, Eve, & George DeLange

Silverleaf Nightshade is more commonly seen. Purple flowers are pretty, fruits look like mini-tomatoes. Again, though, keep kids, pets, tourists, pet-tourists away from these plants. The fruits are particularly tempting to young children, as they are within reach.
Note the 3 Fs for Nightshades: relatively large foliage, 5-fused petaled flowers, tomato-like fruits.