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	$208.87	8.320%	$226.248	$226.25	$226.25	$226.20
Purchase #2	$88.25	13.205%	$99.9034	$99.90	$99.90	$99.90
Purchase #3	$120.68	5.588%	$127.4236	$127.42	$127.40	$127.40
Purchase #4	$122.97	6.208%	$130.604	$130.60	$130.60	$130.60
Purchase #5	$18.75	10.240%	$20.67	$20.67	$20.65	$20.70
Purchase #6	$63.90	12.679%	$72.0019	$72.00	$72.00	$72.00
Purchase #7	$121.89	4.484%	$127.3555	$127.36	$127.35	$127.40
7 purchase totals =	$745.31		$804.2064	$804.20	$804.15	$804.20