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	$116.81	11.675%	$130.4476	$130.45	$130.45	$130.40
Purchase #2	$47.77	4.428%	$49.8853	$49.89	$49.90	$49.90
Purchase #3	$235.25	7.499%	$252.8914	$252.89	$252.90	$252.90
Purchase #4	$26.68	3.184%	$27.5295	$27.53	$27.55	$27.50
Purchase #5	$39.38	8.495%	$42.7253	$42.73	$42.75	$42.70
Purchase #6	$13.97	7.789%	$15.0581	$15.06	$15.05	$15.10
Purchase #7	$127.51	12.515%	$143.4679	$143.47	$143.45	$143.50
7 purchase totals =	$607.37		$662.0051	$662.02	$662.05	$662.00