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	$116.51	10.605%	$128.8659	$128.87	$128.85	$128.90
Purchase #2	$34.87	9.145%	$38.0589	$38.06	$38.05	$38.10
Purchase #3	$97.32	3.245%	$100.478	$100.48	$100.50	$100.50
Purchase #4	$61.58	6.188%	$65.3906	$65.39	$65.40	$65.40
Purchase #5	$186.62	9.837%	$204.9778	$204.98	$205.00	$205.00
Purchase #6	$50.91	5.690%	$53.8068	$53.81	$53.80	$53.80
Purchase #7	$99.48	8.649%	$108.084	$108.08	$108.10	$108.10
7 purchase totals =	$647.29		$699.6620	$699.67	$699.70	$699.80