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	$18.27	5.456%	$19.2668	$19.27	$19.25	$19.30
Purchase #2	$9.88	4.302%	$10.305	$10.31	$10.30	$10.30
Purchase #3	$72.93	7.140%	$78.1372	$78.14	$78.15	$78.10
Purchase #4	$121.97	4.801%	$127.8258	$127.83	$127.85	$127.80
Purchase #5	$109.60	10.790%	$121.4258	$121.43	$121.45	$121.40
Purchase #6	$157.27	13.833%	$179.0252	$179.03	$179.05	$179.00
Purchase #7	$122.28	13.244%	$138.4748	$138.47	$138.45	$138.50
7 purchase totals =	$612.20		$674.4606	$674.48	$674.50	$674.40