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	7.487%	$168.6686	$168.67	$168.65	$168.70
Purchase #2	$98.73	13.316%	$111.8769	$111.88	$111.90	$111.90
Purchase #3	$71.42	8.341%	$77.3771	$77.38	$77.40	$77.40
Purchase #4	$158.54	9.125%	$173.0068	$173.01	$173.00	$173.00
Purchase #5	$63.81	4.204%	$66.4926	$66.49	$66.50	$66.50
Purchase #6	$93.79	8.134%	$101.4189	$101.42	$101.40	$101.40
Purchase #7	$175.85	9.404%	$192.3869	$192.39	$192.40	$192.40
7 purchase totals =	$819.06		$891.2278	$891.24	$891.25	$891.30