Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$90.83	3.683%	$94.1753	$94.18	$94.20	$94.20
Purchase #2	$46.89	8.814%	$51.0229	$51.02	$51.00	$51.00
Purchase #3	$10.49	8.518%	$11.3835	$11.38	$11.40	$11.40
Purchase #4	$101.65	10.756%	$112.5835	$112.58	$112.60	$112.60
Purchase #5	$84.83	11.389%	$94.4913	$94.49	$94.50	$94.50
Purchase #6	$122.27	9.421%	$133.7891	$133.79	$133.80	$133.80
Purchase #7	$92.55	8.662%	$100.5667	$100.57	$100.55	$100.60
7 purchase totals =	$549.51		$598.0123	$598.01	$598.05	$598.10