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	$28.73	11.717%	$32.0963	$32.10	$32.10	$32.10
Purchase #2	$45.87	8.467%	$49.7538	$49.75	$49.75	$49.80
Purchase #3	$233.90	9.427%	$255.9498	$255.95	$255.95	$255.90
Purchase #4	$239.43	11.283%	$266.4449	$266.44	$266.45	$266.40
Purchase #5	$111.38	10.871%	$123.4881	$123.49	$123.50	$123.50
Purchase #6	$239.82	4.842%	$251.4321	$251.43	$251.45	$251.40
Purchase #7	$39.32	11.721%	$43.9287	$43.93	$43.95	$43.90
7 purchase totals =	$938.45		$1,023.0937	$1,023.09	$1,023.15	$1,023.00