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	$151.82	4.522%	$158.6853	$158.69	$158.70	$158.70
Purchase #2	$126.62	11.588%	$141.2927	$141.29	$141.30	$141.30
Purchase #3	$122.45	5.636%	$129.3513	$129.35	$129.35	$129.40
Purchase #4	$144.29	12.806%	$162.7678	$162.77	$162.75	$162.80
Purchase #5	$138.62	4.174%	$144.406	$144.41	$144.40	$144.40
Purchase #6	$131.41	6.239%	$139.6087	$139.61	$139.60	$139.60
Purchase #7	$162.98	13.403%	$184.8242	$184.82	$184.80	$184.80
7 purchase totals =	$978.19		$1,060.9360	$1,060.94	$1,060.90	$1,061.00