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	$100.40	13.655%	$114.1096	$114.11	$114.10	$114.10
Purchase #2	$130.82	10.137%	$144.0812	$144.08	$144.10	$144.10
Purchase #3	$85.85	4.581%	$89.7828	$89.78	$89.80	$89.80
Purchase #4	$86.51	5.467%	$91.2395	$91.24	$91.25	$91.20
Purchase #5	$13.83	11.298%	$15.3925	$15.39	$15.40	$15.40
Purchase #6	$50.75	11.262%	$56.4655	$56.47	$56.45	$56.50
Purchase #7	$103.81	12.837%	$117.1361	$117.14	$117.15	$117.10
7 purchase totals =	$571.97		$628.2072	$628.21	$628.25	$628.20