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	$198.56	9.425%	$217.2743	$217.27	$217.25	$217.30
Purchase #2	$127.25	6.256%	$135.2108	$135.21	$135.20	$135.20
Purchase #3	$78.75	13.611%	$89.4687	$89.47	$89.45	$89.50
Purchase #4	$248.49	8.345%	$269.2265	$269.23	$269.25	$269.20
Purchase #5	$217.63	5.733%	$230.1067	$230.11	$230.10	$230.10
Purchase #6	$113.75	11.624%	$126.9723	$126.97	$126.95	$127.00
Purchase #7	$90.63	11.137%	$100.7235	$100.72	$100.70	$100.70
7 purchase totals =	$1,075.06		$1,168.9828	$1,168.98	$1,168.90	$1,169.00