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	$97.94	5.760%	$103.5813	$103.58	$103.60	$103.60
Purchase #2	$191.62	6.580%	$204.2286	$204.23	$204.25	$204.20
Purchase #3	$93.53	6.731%	$99.8255	$99.83	$99.85	$99.80
Purchase #4	$146.86	12.857%	$165.7418	$165.74	$165.75	$165.70
Purchase #5	$162.42	6.288%	$172.633	$172.63	$172.65	$172.60
Purchase #6	$17.81	9.594%	$19.5187	$19.52	$19.50	$19.50
Purchase #7	$44.71	10.208%	$49.274	$49.27	$49.25	$49.30
7 purchase totals =	$754.89		$814.8029	$814.80	$814.85	$814.70