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	$151.72	12.816%	$171.1644	$171.16	$171.15	$171.20
Purchase #2	$219.97	12.301%	$247.0285	$247.03	$247.05	$247.00
Purchase #3	$159.79	12.579%	$179.89	$179.89	$179.90	$179.90
Purchase #4	$247.71	4.733%	$259.4341	$259.43	$259.45	$259.40
Purchase #5	$143.55	7.172%	$153.8454	$153.85	$153.85	$153.80
Purchase #6	$67.72	4.342%	$70.6604	$70.66	$70.65	$70.70
Purchase #7	$76.43	11.147%	$84.9497	$84.95	$84.95	$84.90
7 purchase totals =	$1,066.89		$1,166.9725	$1,166.97	$1,167.00	$1,166.90