Simple solution. Raise the Oahu GE Tax another .5%, making it an even 5% instead of the present 4.5%.
No matter what rate they tell you the excise taxes are calculated at, it's always more. The state charges you tax on top of the tax.
The current rate is 4% for consumers. Additionally, there is a surcharge tacked on at 0.5% in Honolulu and Kauai, and 0.25% for Hawaii Island.
Even if you added another 0.5% to Honolulu, you still wind up paying more than 5% total.
So, the actual tax rate for Honolulu consumers is 4.712% including the 0.5% surcharge. It's more than the tax rate because businesses owe tax on the entire transaction amount including the tax -- tax on top of tax.
Plus, if you consider everyone who touched that product you bought had to pay taxes (which they passed on to the next person), the consumer is paying multiple times any increase. The 4% tax turns into as much as 12% for the consumer to pay, most of which is rolled up in the price.