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	$212.72	8.634%	$231.0862	$231.09	$231.10	$231.10
Purchase #2	$165.54	7.873%	$178.573	$178.57	$178.55	$178.60
Purchase #3	$59.72	11.162%	$66.3859	$66.39	$66.40	$66.40
Purchase #4	$238.74	13.790%	$271.6622	$271.66	$271.65	$271.70
Purchase #5	$46.65	4.192%	$48.6056	$48.61	$48.60	$48.60
Purchase #6	$189.42	5.855%	$200.5105	$200.51	$200.50	$200.50
Purchase #7	$240.55	13.705%	$273.5174	$273.52	$273.50	$273.50
7 purchase totals =	$1,153.34		$1,270.3408	$1,270.35	$1,270.30	$1,270.40