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	$47.65	11.574%	$53.165	$53.17	$53.15	$53.20
Purchase #2	$10.34	8.171%	$11.1849	$11.18	$11.20	$11.20
Purchase #3	$92.45	12.733%	$104.2217	$104.22	$104.20	$104.20
Purchase #4	$148.70	3.608%	$154.0651	$154.07	$154.05	$154.10
Purchase #5	$27.30	7.702%	$29.4026	$29.40	$29.40	$29.40
Purchase #6	$102.51	8.815%	$111.5463	$111.55	$111.55	$111.50
Purchase #7	$92.83	3.234%	$95.8321	$95.83	$95.85	$95.80
7 purchase totals =	$521.78		$559.4177	$559.42	$559.40	$559.40