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	$192.35	13.206%	$217.7517	$217.75	$217.75	$217.80
Purchase #2	$249.51	4.863%	$261.6437	$261.64	$261.65	$261.60
Purchase #3	$145.72	5.594%	$153.8716	$153.87	$153.85	$153.90
Purchase #4	$191.36	13.302%	$216.8147	$216.81	$216.80	$216.80
Purchase #5	$120.69	5.672%	$127.5355	$127.54	$127.55	$127.50
Purchase #6	$173.56	11.115%	$192.8512	$192.85	$192.85	$192.90
Purchase #7	$65.53	9.530%	$71.775	$71.78	$71.80	$71.80
7 purchase totals =	$1,138.72		$1,242.2434	$1,242.24	$1,242.25	$1,242.30