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	$94.69	11.682%	$105.7517	$105.75	$105.75	$105.80
Purchase #2	$158.65	3.746%	$164.593	$164.59	$164.60	$164.60
Purchase #3	$54.77	12.197%	$61.4503	$61.45	$61.45	$61.50
Purchase #4	$212.51	13.537%	$241.2775	$241.28	$241.30	$241.30
Purchase #5	$39.54	8.756%	$43.0021	$43.00	$43.00	$43.00
Purchase #6	$23.54	6.774%	$25.1346	$25.13	$25.15	$25.10
Purchase #7	$106.51	7.831%	$114.8508	$114.85	$114.85	$114.90
7 purchase totals =	$690.21		$756.0600	$756.05	$756.10	$756.20