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	$61.28	7.465%	$65.8546	$65.85	$65.85	$65.90
Purchase #2	$127.48	9.509%	$139.6021	$139.60	$139.60	$139.60
Purchase #3	$91.69	9.458%	$100.362	$100.36	$100.35	$100.40
Purchase #4	$17.82	10.734%	$19.7328	$19.73	$19.75	$19.70
Purchase #5	$42.96	6.271%	$45.654	$45.65	$45.65	$45.70
Purchase #6	$227.45	11.185%	$252.8903	$252.89	$252.90	$252.90
Purchase #7	$48.60	11.400%	$54.1404	$54.14	$54.15	$54.10
7 purchase totals =	$617.28		$678.2362	$678.22	$678.25	$678.30