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	$159.79	9.847%	$175.5245	$175.52	$175.50	$175.50
Purchase #2	$112.65	5.439%	$118.777	$118.78	$118.80	$118.80
Purchase #3	$244.37	11.171%	$271.6686	$271.67	$271.65	$271.70
Purchase #4	$238.32	7.321%	$255.7674	$255.77	$255.75	$255.80
Purchase #5	$145.91	7.357%	$156.6446	$156.64	$156.65	$156.60
Purchase #6	$72.51	5.384%	$76.4139	$76.41	$76.40	$76.40
Purchase #7	$97.81	10.479%	$108.0595	$108.06	$108.05	$108.10
7 purchase totals =	$1,071.36		$1,162.8555	$1,162.85	$1,162.80	$1,162.90