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	$241.74	12.749%	$272.5594	$272.56	$272.55	$272.60
Purchase #2	$138.34	7.308%	$148.4499	$148.45	$148.45	$148.40
Purchase #3	$5.62	8.114%	$6.076	$6.08	$6.10	$6.10
Purchase #4	$63.52	12.174%	$71.2529	$71.25	$71.25	$71.30
Purchase #5	$70.68	9.635%	$77.49	$77.49	$77.50	$77.50
Purchase #6	$242.84	11.835%	$271.5801	$271.58	$271.60	$271.60
Purchase #7	$222.54	7.174%	$238.505	$238.51	$238.50	$238.50
7 purchase totals =	$985.28		$1,085.9133	$1,085.92	$1,085.95	$1,086.00