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	$56.45	11.421%	$62.8972	$62.90	$62.90	$62.90
Purchase #2	$161.53	4.156%	$168.2432	$168.24	$168.25	$168.20
Purchase #3	$143.48	13.279%	$162.5327	$162.53	$162.55	$162.50
Purchase #4	$129.91	11.456%	$144.7925	$144.79	$144.80	$144.80
Purchase #5	$19.99	12.169%	$22.4226	$22.42	$22.40	$22.40
Purchase #6	$35.75	13.599%	$40.6116	$40.61	$40.60	$40.60
Purchase #7	$15.64	9.256%	$17.0876	$17.09	$17.10	$17.10
7 purchase totals =	$562.75		$618.5874	$618.58	$618.60	$618.50