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	$144.82	7.536%	$155.7336	$155.73	$155.75	$155.70
Purchase #2	$9.78	11.297%	$10.8848	$10.88	$10.90	$10.90
Purchase #3	$102.78	5.318%	$108.2458	$108.25	$108.25	$108.20
Purchase #4	$89.81	11.491%	$100.1301	$100.13	$100.15	$100.10
Purchase #5	$178.87	8.478%	$194.0346	$194.03	$194.05	$194.00
Purchase #6	$127.86	7.468%	$137.4086	$137.41	$137.40	$137.40
Purchase #7	$158.59	4.494%	$165.717	$165.72	$165.70	$165.70
7 purchase totals =	$812.51		$872.1545	$872.15	$872.20	$872.00