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	$138.38	8.495%	$150.1354	$150.14	$150.15	$150.10
Purchase #2	$89.99	9.549%	$98.5831	$98.58	$98.60	$98.60
Purchase #3	$214.92	12.528%	$241.8452	$241.85	$241.85	$241.80
Purchase #4	$124.64	5.181%	$131.0976	$131.10	$131.10	$131.10
Purchase #5	$142.29	6.386%	$151.3766	$151.38	$151.40	$151.40
Purchase #6	$158.64	5.327%	$167.0908	$167.09	$167.10	$167.10
Purchase #7	$205.27	12.504%	$230.937	$230.94	$230.95	$230.90
7 purchase totals =	$1,074.13		$1,171.0657	$1,171.08	$1,171.15	$1,171.00