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	$14.27	8.341%	$15.4603	$15.46	$15.45	$15.50
Purchase #2	$91.68	8.453%	$99.4297	$99.43	$99.45	$99.40
Purchase #3	$145.85	5.602%	$154.0205	$154.02	$154.00	$154.00
Purchase #4	$125.65	4.868%	$131.7666	$131.77	$131.75	$131.80
Purchase #5	$207.43	12.739%	$233.8545	$233.85	$233.85	$233.90
Purchase #6	$74.28	12.205%	$83.3459	$83.35	$83.35	$83.30
Purchase #7	$179.36	5.559%	$189.3306	$189.33	$189.35	$189.30
7 purchase totals =	$838.52		$907.2081	$907.21	$907.20	$907.20