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	$145.40	4.198%	$151.5039	$151.50	$151.50	$151.50
Purchase #2	$29.85	5.839%	$31.5929	$31.59	$31.60	$31.60
Purchase #3	$204.82	12.720%	$230.8731	$230.87	$230.85	$230.90
Purchase #4	$216.58	11.464%	$241.4087	$241.41	$241.40	$241.40
Purchase #5	$54.45	9.602%	$59.6783	$59.68	$59.70	$59.70
Purchase #6	$19.77	4.540%	$20.6676	$20.67	$20.65	$20.70
Purchase #7	$228.81	5.102%	$240.4839	$240.48	$240.50	$240.50
7 purchase totals =	$899.68		$976.2084	$976.20	$976.20	$976.30