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	$163.63	5.248%	$172.2173	$172.22	$172.20	$172.20
Purchase #2	$65.51	3.221%	$67.6201	$67.62	$67.60	$67.60
Purchase #3	$177.62	10.481%	$196.2364	$196.24	$196.25	$196.20
Purchase #4	$119.94	9.548%	$131.3919	$131.39	$131.40	$131.40
Purchase #5	$65.77	4.675%	$68.8447	$68.84	$68.85	$68.80
Purchase #6	$120.94	13.348%	$137.0831	$137.08	$137.10	$137.10
Purchase #7	$149.71	4.188%	$155.9799	$155.98	$156.00	$156.00
7 purchase totals =	$863.12		$929.3734	$929.37	$929.40	$929.30