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	$11.94	4.448%	$12.4711	$12.47	$12.45	$12.50
Purchase #2	$9.95	7.826%	$10.7287	$10.73	$10.75	$10.70
Purchase #3	$81.58	5.777%	$86.2929	$86.29	$86.30	$86.30
Purchase #4	$90.84	13.819%	$103.3932	$103.39	$103.40	$103.40
Purchase #5	$228.34	8.787%	$248.4042	$248.40	$248.40	$248.40
Purchase #6	$224.73	11.278%	$250.075	$250.08	$250.10	$250.10
Purchase #7	$20.29	3.790%	$21.059	$21.06	$21.05	$21.10
7 purchase totals =	$667.67		$732.4241	$732.42	$732.45	$732.50