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	$101.26	3.336%	$104.638	$104.64	$104.65	$104.60
Purchase #2	$186.63	11.527%	$208.1428	$208.14	$208.15	$208.10
Purchase #3	$99.31	4.294%	$103.5744	$103.57	$103.55	$103.60
Purchase #4	$130.57	10.733%	$144.5841	$144.58	$144.60	$144.60
Purchase #5	$81.35	11.162%	$90.4303	$90.43	$90.45	$90.40
Purchase #6	$195.32	7.600%	$210.1643	$210.16	$210.15	$210.20
Purchase #7	$20.65	10.359%	$22.7891	$22.79	$22.80	$22.80
7 purchase totals =	$815.09		$884.3230	$884.31	$884.35	$884.30