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	$220.41	4.540%	$230.4166	$230.42	$230.40	$230.40
Purchase #2	$60.44	6.874%	$64.5946	$64.59	$64.60	$64.60
Purchase #3	$177.77	4.401%	$185.5937	$185.59	$185.60	$185.60
Purchase #4	$233.75	3.177%	$241.1762	$241.18	$241.20	$241.20
Purchase #5	$12.53	13.367%	$14.2049	$14.20	$14.20	$14.20
Purchase #6	$240.40	8.798%	$261.5504	$261.55	$261.55	$261.60
Purchase #7	$94.57	6.133%	$100.37	$100.37	$100.35	$100.40
7 purchase totals =	$1,039.87		$1,097.9064	$1,097.90	$1,097.90	$1,098.00