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	$149.45	4.788%	$156.6057	$156.61	$156.60	$156.60
Purchase #2	$43.85	11.393%	$48.8458	$48.85	$48.85	$48.80
Purchase #3	$92.92	11.407%	$103.5194	$103.52	$103.50	$103.50
Purchase #4	$99.42	12.711%	$112.0573	$112.06	$112.05	$112.10
Purchase #5	$106.25	6.870%	$113.5494	$113.55	$113.55	$113.50
Purchase #6	$148.95	7.253%	$159.7533	$159.75	$159.75	$159.80
Purchase #7	$31.94	8.675%	$34.7108	$34.71	$34.70	$34.70
7 purchase totals =	$672.78		$729.0417	$729.05	$729.00	$729.00