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	$108.90	3.142%	$112.3216	$112.32	$112.30	$112.30
Purchase #2	$77.93	4.260%	$81.2498	$81.25	$81.25	$81.20
Purchase #3	$116.33	9.671%	$127.5803	$127.58	$127.60	$127.60
Purchase #4	$205.47	13.530%	$233.2701	$233.27	$233.25	$233.30
Purchase #5	$122.94	6.278%	$130.6582	$130.66	$130.65	$130.70
Purchase #6	$230.87	4.843%	$242.051	$242.05	$242.05	$242.10
Purchase #7	$152.94	11.265%	$170.1687	$170.17	$170.15	$170.20
7 purchase totals =	$1,015.38		$1,097.2997	$1,097.30	$1,097.25	$1,097.40