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	$231.39	10.313%	$255.2533	$255.25	$255.25	$255.30
Purchase #2	$71.76	8.586%	$77.9213	$77.92	$77.90	$77.90
Purchase #3	$97.93	3.490%	$101.3478	$101.35	$101.35	$101.30
Purchase #4	$216.77	11.538%	$241.7809	$241.78	$241.80	$241.80
Purchase #5	$211.64	13.647%	$240.5225	$240.52	$240.50	$240.50
Purchase #6	$178.49	12.321%	$200.4818	$200.48	$200.50	$200.50
Purchase #7	$214.47	7.328%	$230.1864	$230.19	$230.20	$230.20
7 purchase totals =	$1,222.45		$1,347.4940	$1,347.49	$1,347.50	$1,347.50