Retailers' second-quarter earnings season is poised to begin in mid-August, and it may look a bit like a sandcastle being reclaimed by the sea: lumpy, all over the place, and with plenty of moving parts.

Although oil prices have come down from their spring peak, gasoline remains pricey across the country, well over $4 a gallon, roughly a dollar higher than a year ago, according to AAA.

That's a problem for consumers and also adds to transportation and other input costs for goods. Tariff rates have come down and retailers are anticipating tariff refunds, but at the same time retailers are feeling pressure to lower their prices, rather than just pocket those checks.

All that means that this earnings season, investors may be less likely to be interested in margins, which could get a temporary boost from tariff refunds, and more interested in sales and the overall sustainability of retailers' growth, posits Bernstein analyst Zhihan Ma.

Tariff costs were high a year ago, so lapping that metric, along with refunds, means that companies from Five Below to Dollar Tree and even potentially Target could notch big margin beats, she estimates; Walmart is expected to get some $3 billion in tariff refunds alone, which could help offset fuel inflation and price cuts.

Yet Wall Street is feeling nervous about the world's largest retailer, as comparable sales may be weak. Inflation has led to some pullback in its general merchandise sales ( Tractor Supply noted weak demand in May), while grocery stores like Albertsons have likewise warned that lower income shoppers were feeling the pinch.

Interestingly, that hasn't extended to dollar stores, Ma notes, with investor sentiment largely positive on companies like Dollar General and Dollar Tree, which haven't offered similarly cautious commentary, despite a difficult first quarter. The hope is that the backdrop and the weak start to the year can be a "springboard" for their comeback.

Yet there may be more at play, she writes. One theory is that Walmart has high exposure to the southern U.S., where fuel inflation has been particularly pronounced.

"Its core low income consumers in the South may be more reluctant to drive to a supercenter and instead opt to shop online or in nearby stores (including dollar stores) within walking distance," she writes. "The other is the headwind from drug price deflation, which affects Albertsons and Kroger as well, but doesn't move the needle for dollar [stores and] has little impact on bottom line, so the comp impact is purely optical."

Overall, though, she is still upbeat about Walmart, reiterating an Outperform rating despite lowering her price target by $3 to $142, and writes that any post-earnings weakness is a buying opportunity, particularly as worries about comparable sales weakness appear overblown.

Dollar General and Five Below are her discounter picks: she has an Outperform rating on both, and price targets of $149 and $250, respectively, noting that both may deliver better-than-expected revenue in the second quarter. She has Market Perform ratings on Target and Dollar Tree.

Time will tell whether sales will matter more than tariff-inflated margins. Retail reports begin Aug. 19 with Target's report, followed by Walmart the next day.