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	$154.73	4.691%	$161.9884	$161.99	$162.00	$162.00
Purchase #2	$44.92	13.855%	$51.1437	$51.14	$51.15	$51.10
Purchase #3	$153.83	7.647%	$165.5934	$165.59	$165.60	$165.60
Purchase #4	$84.74	6.293%	$90.0727	$90.07	$90.05	$90.10
Purchase #5	$136.76	5.788%	$144.6757	$144.68	$144.70	$144.70
Purchase #6	$49.25	6.500%	$52.4513	$52.45	$52.45	$52.50
Purchase #7	$83.63	8.383%	$90.6407	$90.64	$90.65	$90.60
7 purchase totals =	$707.86		$756.5659	$756.56	$756.60	$756.60