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	$62.63	7.335%	$67.2239	$67.22	$67.20	$67.20
Purchase #2	$117.59	8.612%	$127.7169	$127.72	$127.70	$127.70
Purchase #3	$44.42	13.655%	$50.4856	$50.49	$50.50	$50.50
Purchase #4	$51.87	4.656%	$54.2851	$54.29	$54.30	$54.30
Purchase #5	$214.83	12.613%	$241.9265	$241.93	$241.95	$241.90
Purchase #6	$170.68	4.714%	$178.7259	$178.73	$178.75	$178.70
Purchase #7	$212.87	11.269%	$236.8583	$236.86	$236.85	$236.90
7 purchase totals =	$874.89		$957.2222	$957.24	$957.25	$957.20