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	$154.47	3.193%	$159.4022	$159.40	$159.40	$159.40
Purchase #2	$47.44	9.622%	$52.0047	$52.00	$52.00	$52.00
Purchase #3	$18.62	10.538%	$20.5822	$20.58	$20.60	$20.60
Purchase #4	$87.62	3.215%	$90.437	$90.44	$90.45	$90.40
Purchase #5	$98.58	6.665%	$105.1504	$105.15	$105.15	$105.20
Purchase #6	$95.58	11.182%	$106.2678	$106.27	$106.25	$106.30
Purchase #7	$207.98	11.746%	$232.4093	$232.41	$232.40	$232.40
7 purchase totals =	$710.29		$766.2536	$766.25	$766.25	$766.30