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	$149.52	3.484%	$154.7293	$154.73	$154.75	$154.70
Purchase #2	$131.83	11.134%	$146.508	$146.51	$146.50	$146.50
Purchase #3	$129.73	10.406%	$143.2297	$143.23	$143.25	$143.20
Purchase #4	$85.74	5.494%	$90.4506	$90.45	$90.45	$90.50
Purchase #5	$148.32	4.256%	$154.6325	$154.63	$154.65	$154.60
Purchase #6	$130.58	11.201%	$145.2063	$145.21	$145.20	$145.20
Purchase #7	$63.55	3.532%	$65.7946	$65.79	$65.80	$65.80
7 purchase totals =	$839.27		$900.5510	$900.55	$900.60	$900.50