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	$143.76	5.229%	$151.2772	$151.28	$151.30	$151.30
Purchase #2	$60.98	6.690%	$65.0596	$65.06	$65.05	$65.10
Purchase #3	$195.57	13.192%	$221.3696	$221.37	$221.35	$221.40
Purchase #4	$94.98	10.794%	$105.2321	$105.23	$105.25	$105.20
Purchase #5	$129.98	7.292%	$139.4581	$139.46	$139.45	$139.50
Purchase #6	$197.51	8.558%	$214.4129	$214.41	$214.40	$214.40
Purchase #7	$99.25	6.654%	$105.8541	$105.85	$105.85	$105.90
7 purchase totals =	$922.03		$1,002.6636	$1,002.66	$1,002.65	$1,002.80