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	$112.30	10.394%	$123.9725	$123.97	$123.95	$124.00
Purchase #2	$25.60	13.567%	$29.0732	$29.07	$29.05	$29.10
Purchase #3	$50.39	8.536%	$54.6913	$54.69	$54.70	$54.70
Purchase #4	$19.63	8.682%	$21.3343	$21.33	$21.35	$21.30
Purchase #5	$102.28	6.155%	$108.5753	$108.58	$108.60	$108.60
Purchase #6	$9.70	4.365%	$10.1234	$10.12	$10.10	$10.10
Purchase #7	$103.89	7.434%	$111.6132	$111.61	$111.60	$111.60
7 purchase totals =	$423.79		$459.3832	$459.37	$459.35	$459.40