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	$81.97	5.476%	$86.4587	$86.46	$86.45	$86.50
Purchase #2	$45.65	9.590%	$50.0278	$50.03	$50.05	$50.00
Purchase #3	$87.61	5.109%	$92.086	$92.09	$92.10	$92.10
Purchase #4	$116.46	13.469%	$132.146	$132.15	$132.15	$132.10
Purchase #5	$192.47	3.540%	$199.2834	$199.28	$199.30	$199.30
Purchase #6	$119.51	6.522%	$127.3044	$127.30	$127.30	$127.30
Purchase #7	$26.25	4.664%	$27.4743	$27.47	$27.45	$27.50
7 purchase totals =	$669.92		$714.7806	$714.78	$714.80	$714.80