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	$230.30	3.552%	$238.4803	$238.48	$238.50	$238.50
Purchase #2	$44.77	3.846%	$46.4919	$46.49	$46.50	$46.50
Purchase #3	$109.25	3.766%	$113.3644	$113.36	$113.35	$113.40
Purchase #4	$11.79	5.806%	$12.4745	$12.47	$12.45	$12.50
Purchase #5	$79.68	11.857%	$89.1277	$89.13	$89.15	$89.10
Purchase #6	$83.86	3.563%	$86.8479	$86.85	$86.85	$86.80
Purchase #7	$195.64	9.734%	$214.6836	$214.68	$214.70	$214.70
7 purchase totals =	$755.29		$801.4703	$801.46	$801.50	$801.50