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	$116.70	8.459%	$126.5717	$126.57	$126.55	$126.60
Purchase #2	$99.74	6.163%	$105.887	$105.89	$105.90	$105.90
Purchase #3	$92.76	12.769%	$104.6045	$104.60	$104.60	$104.60
Purchase #4	$145.72	13.860%	$165.9168	$165.92	$165.90	$165.90
Purchase #5	$50.52	11.334%	$56.2459	$56.25	$56.25	$56.20
Purchase #6	$30.57	13.866%	$34.8088	$34.81	$34.80	$34.80
Purchase #7	$99.91	5.137%	$105.0424	$105.04	$105.05	$105.00
7 purchase totals =	$635.92		$699.0771	$699.08	$699.05	$699.00