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	$127.86	11.874%	$143.0421	$143.04	$143.05	$143.00
Purchase #2	$121.26	9.406%	$132.6657	$132.67	$132.65	$132.70
Purchase #3	$29.34	11.228%	$32.6343	$32.63	$32.65	$32.60
Purchase #4	$76.61	8.452%	$83.0851	$83.09	$83.10	$83.10
Purchase #5	$112.83	13.120%	$127.6333	$127.63	$127.65	$127.60
Purchase #6	$7.58	13.591%	$8.6102	$8.61	$8.60	$8.60
Purchase #7	$62.91	3.755%	$65.2723	$65.27	$65.25	$65.30
7 purchase totals =	$538.39		$592.9430	$592.94	$592.95	$592.90