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	$80.59	3.572%	$83.4687	$83.47	$83.45	$83.50
Purchase #2	$148.98	11.830%	$166.6043	$166.60	$166.60	$166.60
Purchase #3	$139.75	13.164%	$158.1467	$158.15	$158.15	$158.10
Purchase #4	$241.52	5.185%	$254.0428	$254.04	$254.05	$254.00
Purchase #5	$103.70	4.584%	$108.4536	$108.45	$108.45	$108.50
Purchase #6	$49.86	9.532%	$54.6127	$54.61	$54.60	$54.60
Purchase #7	$208.43	9.468%	$228.1642	$228.16	$228.15	$228.20
7 purchase totals =	$972.83		$1,053.4930	$1,053.48	$1,053.45	$1,053.50