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	$232.37	10.853%	$257.5891	$257.59	$257.60	$257.60
Purchase #2	$90.42	10.449%	$99.868	$99.87	$99.85	$99.90
Purchase #3	$235.41	11.238%	$261.8654	$261.87	$261.85	$261.90
Purchase #4	$5.27	7.302%	$5.6548	$5.65	$5.65	$5.70
Purchase #5	$101.76	7.140%	$109.0257	$109.03	$109.05	$109.00
Purchase #6	$49.45	10.508%	$54.6462	$54.65	$54.65	$54.60
Purchase #7	$132.79	9.366%	$145.2271	$145.23	$145.25	$145.20
7 purchase totals =	$847.47		$933.8763	$933.89	$933.90	$933.90