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	$156.92	10.560%	$173.4908	$173.49	$173.50	$173.50
Purchase #2	$140.91	4.765%	$147.6244	$147.62	$147.60	$147.60
Purchase #3	$36.45	7.452%	$39.1663	$39.17	$39.15	$39.20
Purchase #4	$95.71	5.246%	$100.7309	$100.73	$100.75	$100.70
Purchase #5	$139.63	8.445%	$151.4218	$151.42	$151.40	$151.40
Purchase #6	$233.71	5.749%	$247.146	$247.15	$247.15	$247.10
Purchase #7	$168.49	11.660%	$188.1359	$188.14	$188.15	$188.10
7 purchase totals =	$971.82		$1,047.7161	$1,047.72	$1,047.70	$1,047.60