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	$146.50	5.505%	$154.5648	$154.56	$154.55	$154.60
Purchase #2	$94.58	7.414%	$101.5922	$101.59	$101.60	$101.60
Purchase #3	$17.97	7.302%	$19.2822	$19.28	$19.30	$19.30
Purchase #4	$217.73	7.322%	$233.6722	$233.67	$233.65	$233.70
Purchase #5	$74.86	4.438%	$78.1823	$78.18	$78.20	$78.20
Purchase #6	$44.81	12.297%	$50.3203	$50.32	$50.30	$50.30
Purchase #7	$25.95	13.452%	$29.4408	$29.44	$29.45	$29.40
7 purchase totals =	$622.40		$667.0548	$667.04	$667.05	$667.10