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	$63.96	5.642%	$67.5686	$67.57	$67.55	$67.60
Purchase #2	$157.52	5.820%	$166.6877	$166.69	$166.70	$166.70
Purchase #3	$72.60	11.848%	$81.2016	$81.20	$81.20	$81.20
Purchase #4	$10.89	5.327%	$11.4701	$11.47	$11.45	$11.50
Purchase #5	$118.72	7.738%	$127.9066	$127.91	$127.90	$127.90
Purchase #6	$50.30	9.136%	$54.8954	$54.90	$54.90	$54.90
Purchase #7	$201.28	12.359%	$226.1562	$226.16	$226.15	$226.20
7 purchase totals =	$675.27		$735.8862	$735.90	$735.85	$736.00