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	$106.96	9.634%	$117.2645	$117.26	$117.25	$117.30
Purchase #2	$26.77	5.401%	$28.2158	$28.22	$28.20	$28.20
Purchase #3	$95.62	4.282%	$99.7144	$99.71	$99.70	$99.70
Purchase #4	$112.48	13.197%	$127.324	$127.32	$127.30	$127.30
Purchase #5	$136.65	5.415%	$144.0496	$144.05	$144.05	$144.00
Purchase #6	$156.72	5.710%	$165.6687	$165.67	$165.65	$165.70
Purchase #7	$51.38	9.832%	$56.4317	$56.43	$56.45	$56.40
7 purchase totals =	$686.58		$738.6687	$738.66	$738.60	$738.60