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	$161.35	10.329%	$178.0158	$178.02	$178.00	$178.00
Purchase #2	$189.56	10.491%	$209.4467	$209.45	$209.45	$209.40
Purchase #3	$30.66	5.836%	$32.4493	$32.45	$32.45	$32.40
Purchase #4	$10.32	5.150%	$10.8515	$10.85	$10.85	$10.90
Purchase #5	$127.79	7.306%	$137.1263	$137.13	$137.15	$137.10
Purchase #6	$69.61	8.696%	$75.6633	$75.66	$75.65	$75.70
Purchase #7	$85.87	4.145%	$89.4293	$89.43	$89.45	$89.40
7 purchase totals =	$675.16		$732.9822	$732.99	$733.00	$732.90