Build an economy
Keep enough cash for interest and spend when the next blind demands it.
Set a cash target
With the default interest rules, every $5 held at payout earns $1 of interest, up to $5. If the next blind is safe, preserving a multiple of $5 can make the next shop easier.
Avoid empty rerolls
Reroll when you can afford both the reroll and something worth buying. If you already clear the next blind, another shop may be a better place to look for upgrades.
Spend to survive
Interest only matters if the run continues. If your usual hand cannot reach the next target, buy an immediate scoring boost before saving for a dream build.