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	$92.49	6.416%	$98.4242	$98.42	$98.40	$98.40
Purchase #2	$46.61	3.455%	$48.2204	$48.22	$48.20	$48.20
Purchase #3	$136.54	4.117%	$142.1614	$142.16	$142.15	$142.20
Purchase #4	$106.78	7.402%	$114.6839	$114.68	$114.70	$114.70
Purchase #5	$93.54	6.299%	$99.4321	$99.43	$99.45	$99.40
Purchase #6	$51.35	5.593%	$54.222	$54.22	$54.20	$54.20
Purchase #7	$142.25	8.668%	$154.5802	$154.58	$154.60	$154.60
7 purchase totals =	$669.56		$711.7242	$711.71	$711.70	$711.70