This may seem strange to some people because most people use coal tar shampoo to relieve scalp conditions and people mostly care about effectiveness. But when I buy coal tar shampoo, what I care about the most is the scent. Coal tar doesn't have a very pleasant scent, so I look for a shampoo that doesn't smell too bad. I realize that some brands may try to mask the smell of coal tar with synthetic perfumes. I certainly don't want a shampoo loaded with chemicals. But there are shampoos with natural scents and ingredients that help mask the scent of coal tar a little bit.
The only way to know if a shampoo's scent is tolerable is to smell it. Reading customer reviews before buying a shampoo is a good idea too.