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	$82.32	3.404%	$85.1222	$85.12	$85.10	$85.10
Purchase #2	$214.65	10.857%	$237.9546	$237.95	$237.95	$238.00
Purchase #3	$97.55	8.257%	$105.6047	$105.60	$105.60	$105.60
Purchase #4	$98.38	13.433%	$111.5954	$111.60	$111.60	$111.60
Purchase #5	$221.28	13.820%	$251.8609	$251.86	$251.85	$251.90
Purchase #6	$37.42	4.452%	$39.0859	$39.09	$39.10	$39.10
Purchase #7	$30.74	4.491%	$32.1205	$32.12	$32.10	$32.10
7 purchase totals =	$782.34		$863.3442	$863.34	$863.30	$863.40