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	$46.99	13.671%	$53.414	$53.41	$53.40	$53.40
Purchase #2	$16.52	9.634%	$18.1115	$18.11	$18.10	$18.10
Purchase #3	$106.55	4.435%	$111.2755	$111.28	$111.30	$111.30
Purchase #4	$237.62	5.144%	$249.8432	$249.84	$249.85	$249.80
Purchase #5	$88.94	10.716%	$98.4708	$98.47	$98.45	$98.50
Purchase #6	$100.86	3.259%	$104.147	$104.15	$104.15	$104.10
Purchase #7	$46.31	12.426%	$52.0645	$52.06	$52.05	$52.10
7 purchase totals =	$643.79		$687.3265	$687.32	$687.30	$687.30