The way I view it is being able to function under the huge stress and chaos of a retail store, while not making any mistakes, is one of the primary attributes of a good retail pharmacist. Plus, it is survival of the fittest, so you can either learn to deal with it, or you'll have to look for another job.
Some tips... Know your products! Not just top 200 drugs, more like top 1,000+, the more the better, including OTCs, etc. Things to know: brand name, generic name, strengths, dosage forms, indication, usual dosage, bioequivalence, idiosyncrasies.
Knowing these things will make you a lot faster because you it will remove the uncertainty that causes you to second guess yourself, or that keeps you up at night questioning the 'unknown'. You need to be confident and be sure that you dispensed everything correctly.
Now you will eventually memorize these things, but even I find myself having to look things up for the first time, but then I write it down in a notebook and memorize it so I won't have to look it up anymore. For example, I made a note that methylphenidate 30%-70% ER capsule is Metadate CD, while 50%-50% is Ritalin LA.