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	$77.39	7.342%	$83.072	$83.07	$83.05	$83.10
Purchase #2	$34.27	11.754%	$38.2981	$38.30	$38.30	$38.30
Purchase #3	$116.32	9.509%	$127.3809	$127.38	$127.40	$127.40
Purchase #4	$66.72	11.150%	$74.1593	$74.16	$74.15	$74.20
Purchase #5	$70.39	8.841%	$76.6132	$76.61	$76.60	$76.60
Purchase #6	$146.91	5.790%	$155.4161	$155.42	$155.40	$155.40
Purchase #7	$142.94	12.389%	$160.6488	$160.65	$160.65	$160.60
7 purchase totals =	$654.94		$715.5884	$715.59	$715.55	$715.60