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	$56.52	12.211%	$63.4217	$63.42	$63.40	$63.40
Purchase #2	$39.51	9.536%	$43.2777	$43.28	$43.30	$43.30
Purchase #3	$92.69	9.855%	$101.8246	$101.82	$101.80	$101.80
Purchase #4	$235.88	8.383%	$255.6538	$255.65	$255.65	$255.70
Purchase #5	$230.55	6.184%	$244.8072	$244.81	$244.80	$244.80
Purchase #6	$87.73	5.321%	$92.3981	$92.40	$92.40	$92.40
Purchase #7	$229.43	13.401%	$260.1759	$260.18	$260.20	$260.20
7 purchase totals =	$972.31		$1,061.5590	$1,061.56	$1,061.55	$1,061.60