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	$235.46	11.598%	$262.7687	$262.77	$262.75	$262.80
Purchase #2	$213.28	11.834%	$238.5196	$238.52	$238.50	$238.50
Purchase #3	$10.92	7.859%	$11.7782	$11.78	$11.80	$11.80
Purchase #4	$241.88	12.819%	$272.8866	$272.89	$272.90	$272.90
Purchase #5	$28.82	13.733%	$32.7779	$32.78	$32.80	$32.80
Purchase #6	$125.78	9.305%	$137.4838	$137.48	$137.50	$137.50
Purchase #7	$65.83	13.124%	$74.4695	$74.47	$74.45	$74.50
7 purchase totals =	$921.97		$1,030.6843	$1,030.69	$1,030.70	$1,030.80