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	$82.55	11.298%	$91.8765	$91.88	$91.90	$91.90
Purchase #2	$74.31	5.225%	$78.1927	$78.19	$78.20	$78.20
Purchase #3	$31.42	8.703%	$34.1545	$34.15	$34.15	$34.20
Purchase #4	$93.98	13.469%	$106.6382	$106.64	$106.65	$106.60
Purchase #5	$217.53	5.194%	$228.8285	$228.83	$228.85	$228.80
Purchase #6	$59.39	6.338%	$63.1541	$63.15	$63.15	$63.20
Purchase #7	$162.72	12.754%	$183.4733	$183.47	$183.45	$183.50
7 purchase totals =	$721.90		$786.3178	$786.31	$786.35	$786.40