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	$44.61	9.466%	$48.8328	$48.83	$48.85	$48.80
Purchase #2	$160.78	11.560%	$179.3662	$179.37	$179.35	$179.40
Purchase #3	$54.80	4.829%	$57.4463	$57.45	$57.45	$57.40
Purchase #4	$77.53	10.168%	$85.4133	$85.41	$85.40	$85.40
Purchase #5	$79.44	7.145%	$85.116	$85.12	$85.10	$85.10
Purchase #6	$126.71	12.723%	$142.8313	$142.83	$142.85	$142.80
Purchase #7	$115.25	4.151%	$120.034	$120.03	$120.05	$120.00
7 purchase totals =	$659.12		$719.0399	$719.04	$719.05	$718.90