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	$68.84	12.733%	$77.6054	$77.61	$77.60	$77.60
Purchase #2	$119.79	6.393%	$127.4482	$127.45	$127.45	$127.40
Purchase #3	$172.85	10.261%	$190.5861	$190.59	$190.60	$190.60
Purchase #4	$84.87	6.162%	$90.0997	$90.10	$90.10	$90.10
Purchase #5	$236.87	4.684%	$247.965	$247.97	$247.95	$248.00
Purchase #6	$46.32	10.836%	$51.3392	$51.34	$51.35	$51.30
Purchase #7	$64.74	3.531%	$67.026	$67.03	$67.05	$67.00
7 purchase totals =	$794.28		$852.0696	$852.09	$852.10	$852.00