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	$78.92	8.284%	$85.4577	$85.46	$85.45	$85.50
Purchase #2	$97.69	5.667%	$103.2261	$103.23	$103.25	$103.20
Purchase #3	$41.64	12.677%	$46.9187	$46.92	$46.90	$46.90
Purchase #4	$129.60	7.559%	$139.3965	$139.40	$139.40	$139.40
Purchase #5	$241.30	5.426%	$254.3929	$254.39	$254.40	$254.40
Purchase #6	$199.61	10.441%	$220.4513	$220.45	$220.45	$220.50
Purchase #7	$20.68	3.628%	$21.4303	$21.43	$21.45	$21.40
7 purchase totals =	$809.44		$871.2735	$871.28	$871.30	$871.30