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	$127.55	11.800%	$142.6009	$142.60	$142.60	$142.60
Purchase #2	$101.51	13.370%	$115.0819	$115.08	$115.10	$115.10
Purchase #3	$38.85	6.601%	$41.4145	$41.41	$41.40	$41.40
Purchase #4	$221.60	13.652%	$251.8528	$251.85	$251.85	$251.90
Purchase #5	$173.99	3.351%	$179.8204	$179.82	$179.80	$179.80
Purchase #6	$128.79	10.482%	$142.2898	$142.29	$142.30	$142.30
Purchase #7	$106.60	4.828%	$111.7466	$111.75	$111.75	$111.70
7 purchase totals =	$898.89		$984.8069	$984.80	$984.80	$984.80