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	$223.99	4.317%	$233.6596	$233.66	$233.65	$233.70
Purchase #2	$86.93	4.420%	$90.7723	$90.77	$90.75	$90.80
Purchase #3	$99.92	6.709%	$106.6236	$106.62	$106.60	$106.60
Purchase #4	$32.66	3.827%	$33.9099	$33.91	$33.90	$33.90
Purchase #5	$219.49	4.431%	$229.2156	$229.22	$229.20	$229.20
Purchase #6	$248.68	3.509%	$257.4062	$257.41	$257.40	$257.40
Purchase #7	$127.53	7.734%	$137.3932	$137.39	$137.40	$137.40
7 purchase totals =	$1,039.20		$1,088.9804	$1,088.98	$1,088.90	$1,089.00