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	$189.67	13.155%	$214.6211	$214.62	$214.60	$214.60
Purchase #2	$46.32	6.285%	$49.2312	$49.23	$49.25	$49.20
Purchase #3	$77.88	10.532%	$86.0823	$86.08	$86.10	$86.10
Purchase #4	$182.72	11.836%	$204.3467	$204.35	$204.35	$204.30
Purchase #5	$122.32	7.862%	$131.9368	$131.94	$131.95	$131.90
Purchase #6	$240.47	12.536%	$270.6153	$270.62	$270.60	$270.60
Purchase #7	$99.69	11.536%	$111.1902	$111.19	$111.20	$111.20
7 purchase totals =	$959.07		$1,068.0236	$1,068.03	$1,068.05	$1,067.90