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	$10.62	11.442%	$11.8351	$11.84	$11.85	$11.80
Purchase #2	$65.58	10.820%	$72.6758	$72.68	$72.70	$72.70
Purchase #3	$38.97	9.318%	$42.6012	$42.60	$42.60	$42.60
Purchase #4	$5.70	10.262%	$6.2849	$6.28	$6.30	$6.30
Purchase #5	$202.49	12.509%	$227.8195	$227.82	$227.80	$227.80
Purchase #6	$152.43	4.670%	$159.5485	$159.55	$159.55	$159.50
Purchase #7	$99.30	4.296%	$103.5659	$103.57	$103.55	$103.60
7 purchase totals =	$575.09		$624.3309	$624.34	$624.35	$624.30