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	$187.64	9.583%	$205.6215	$205.62	$205.60	$205.60
Purchase #2	$24.50	11.649%	$27.354	$27.35	$27.35	$27.40
Purchase #3	$147.52	11.584%	$164.6087	$164.61	$164.60	$164.60
Purchase #4	$49.74	5.608%	$52.5294	$52.53	$52.55	$52.50
Purchase #5	$39.75	13.406%	$45.0789	$45.08	$45.10	$45.10
Purchase #6	$147.26	7.690%	$158.5843	$158.58	$158.60	$158.60
Purchase #7	$18.48	8.527%	$20.0558	$20.06	$20.05	$20.10
7 purchase totals =	$614.89		$673.8326	$673.83	$673.85	$673.90