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	$244.42	6.323%	$259.8747	$259.87	$259.85	$259.90
Purchase #2	$222.27	11.304%	$247.3954	$247.40	$247.40	$247.40
Purchase #3	$88.59	13.399%	$100.4602	$100.46	$100.45	$100.50
Purchase #4	$105.89	4.872%	$111.049	$111.05	$111.05	$111.00
Purchase #5	$16.88	13.146%	$19.099	$19.10	$19.10	$19.10
Purchase #6	$169.70	3.767%	$176.0926	$176.09	$176.10	$176.10
Purchase #7	$146.43	9.472%	$160.2998	$160.30	$160.30	$160.30
7 purchase totals =	$994.18		$1,074.2707	$1,074.27	$1,074.25	$1,074.30