If this passes and Albertson's, Safeway (same corporation, actually), Fred Meyer, Wal-Mart, Winco, and all their pharmacies pass on the 2.5% increase in costs, that means that the Oregon Trail Card will be able to buy 2.5% less in groceries.  

That means your prescription costs will go up by 2.5%.  That means your diapers, feminine hygiene items, toothpaste, and other personal care items will go up by 2.5%.  

"The average supermarket has a profit margin of about 1 percent, according to Stacey Vanek-Smith of National Public Radio. Some experts suggest this figure might be as high as 3 percent. Either way, supermarkets are a volume business. The extremely thin profit margin in the grocery business comes from the large amount of competition due to the low barrier of entry into the market."  

If those markets have a profit margin of 1%, they will lose 1.5% on every sale with this tax if they don't pass it on to the consumer.