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	$50.43	9.167%	$55.0529	$55.05	$55.05	$55.10
Purchase #2	$95.39	10.608%	$105.509	$105.51	$105.50	$105.50
Purchase #3	$10.69	3.252%	$11.0376	$11.04	$11.05	$11.00
Purchase #4	$72.78	6.573%	$77.5638	$77.56	$77.55	$77.60
Purchase #5	$32.69	11.111%	$36.3222	$36.32	$36.30	$36.30
Purchase #6	$36.34	11.275%	$40.4373	$40.44	$40.45	$40.40
Purchase #7	$179.39	6.622%	$191.2692	$191.27	$191.25	$191.30
7 purchase totals =	$477.71		$517.1920	$517.19	$517.15	$517.20