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	$203.82	3.418%	$210.7866	$210.79	$210.80	$210.80
Purchase #2	$205.36	9.625%	$225.1259	$225.13	$225.15	$225.10
Purchase #3	$27.32	6.398%	$29.0679	$29.07	$29.05	$29.10
Purchase #4	$227.55	6.109%	$241.451	$241.45	$241.45	$241.50
Purchase #5	$103.60	10.316%	$114.2874	$114.29	$114.30	$114.30
Purchase #6	$127.52	9.654%	$139.8308	$139.83	$139.85	$139.80
Purchase #7	$178.65	11.625%	$199.4181	$199.42	$199.40	$199.40
7 purchase totals =	$1,073.82		$1,159.9677	$1,159.98	$1,160.00	$1,160.00