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	$60.62	7.461%	$65.1429	$65.14	$65.15	$65.10
Purchase #2	$50.78	7.867%	$54.7749	$54.77	$54.75	$54.80
Purchase #3	$162.50	10.433%	$179.4536	$179.45	$179.45	$179.50
Purchase #4	$73.43	5.146%	$77.2087	$77.21	$77.20	$77.20
Purchase #5	$185.38	6.581%	$197.5799	$197.58	$197.60	$197.60
Purchase #6	$117.90	8.391%	$127.793	$127.79	$127.80	$127.80
Purchase #7	$23.98	6.260%	$25.4811	$25.48	$25.50	$25.50
7 purchase totals =	$674.59		$727.4341	$727.42	$727.45	$727.50