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	$18.75	4.237%	$19.5444	$19.54	$19.55	$19.50
Purchase #2	$49.53	5.177%	$52.0942	$52.09	$52.10	$52.10
Purchase #3	$18.79	4.773%	$19.6868	$19.69	$19.70	$19.70
Purchase #4	$74.91	10.295%	$82.622	$82.62	$82.60	$82.60
Purchase #5	$183.51	9.233%	$200.4535	$200.45	$200.45	$200.50
Purchase #6	$99.83	6.794%	$106.6125	$106.61	$106.60	$106.60
Purchase #7	$101.28	7.694%	$109.0725	$109.07	$109.05	$109.10
7 purchase totals =	$546.60		$590.0859	$590.07	$590.05	$590.10