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	$146.92	12.407%	$165.1484	$165.15	$165.15	$165.10
Purchase #2	$168.70	10.616%	$186.6092	$186.61	$186.60	$186.60
Purchase #3	$84.65	7.717%	$91.1824	$91.18	$91.20	$91.20
Purchase #4	$250.32	6.287%	$266.0576	$266.06	$266.05	$266.10
Purchase #5	$95.95	11.830%	$107.3009	$107.30	$107.30	$107.30
Purchase #6	$90.46	10.658%	$100.1012	$100.10	$100.10	$100.10
Purchase #7	$122.42	4.441%	$127.8567	$127.86	$127.85	$127.90
7 purchase totals =	$959.42		$1,044.2564	$1,044.26	$1,044.25	$1,044.30