But I thought it's a 99¢ Store....

It's a sign of the times.
Most likely due to the rise in gas and oil prices, 99¢ Stores had to raise the price for many of the items by several cents (between 30¢ to $1) to offset the costs (many of the items sold are coming from outside the US).

Hopefully prices will come down again but that might be wishful thinking.
Once upon a time there were shops called the 5¢ & 10¢ and discount chain stores like Woolworth's but the have closed shop and disappeared...