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	$158.88	11.215%	$176.6984	$176.70	$176.70	$176.70
Purchase #2	$46.54	11.386%	$51.839	$51.84	$51.85	$51.80
Purchase #3	$122.32	5.365%	$128.8825	$128.88	$128.90	$128.90
Purchase #4	$89.29	13.217%	$101.0915	$101.09	$101.10	$101.10
Purchase #5	$81.50	10.510%	$90.0657	$90.07	$90.05	$90.10
Purchase #6	$127.92	5.413%	$134.8443	$134.84	$134.85	$134.80
Purchase #7	$19.53	8.263%	$21.1438	$21.14	$21.15	$21.10
7 purchase totals =	$645.98		$704.5652	$704.56	$704.60	$704.50