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	$94.97	9.147%	$103.6569	$103.66	$103.65	$103.70
Purchase #2	$95.31	5.834%	$100.8704	$100.87	$100.85	$100.90
Purchase #3	$28.71	11.631%	$32.0493	$32.05	$32.05	$32.00
Purchase #4	$243.25	6.796%	$259.7813	$259.78	$259.80	$259.80
Purchase #5	$52.29	4.601%	$54.6959	$54.70	$54.70	$54.70
Purchase #6	$120.83	10.307%	$133.2839	$133.28	$133.30	$133.30
Purchase #7	$13.31	5.873%	$14.0917	$14.09	$14.10	$14.10
7 purchase totals =	$648.67		$698.4294	$698.43	$698.45	$698.50