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	$89.32	13.733%	$101.5863	$101.59	$101.60	$101.60
Purchase #2	$81.27	5.399%	$85.6578	$85.66	$85.65	$85.70
Purchase #3	$21.38	5.671%	$22.5925	$22.59	$22.60	$22.60
Purchase #4	$47.78	3.143%	$49.2817	$49.28	$49.30	$49.30
Purchase #5	$53.77	5.400%	$56.6736	$56.67	$56.65	$56.70
Purchase #6	$214.47	8.815%	$233.3755	$233.38	$233.40	$233.40
Purchase #7	$236.66	4.353%	$246.9618	$246.96	$246.95	$247.00
7 purchase totals =	$744.65		$796.1292	$796.13	$796.15	$796.30