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	$106.82	4.303%	$111.4165	$111.42	$111.40	$111.40
Purchase #2	$57.43	12.772%	$64.765	$64.77	$64.75	$64.80
Purchase #3	$62.37	5.443%	$65.7648	$65.76	$65.75	$65.80
Purchase #4	$204.57	11.382%	$227.8542	$227.85	$227.85	$227.90
Purchase #5	$40.82	6.303%	$43.3929	$43.39	$43.40	$43.40
Purchase #6	$172.28	6.295%	$183.125	$183.13	$183.15	$183.10
Purchase #7	$66.45	7.591%	$71.4942	$71.49	$71.50	$71.50
7 purchase totals =	$710.74		$767.8126	$767.81	$767.80	$767.90