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	$132.54	8.347%	$143.6031	$143.60	$143.60	$143.60
Purchase #2	$85.96	7.717%	$92.5935	$92.59	$92.60	$92.60
Purchase #3	$49.89	6.665%	$53.2152	$53.22	$53.20	$53.20
Purchase #4	$126.60	4.138%	$131.8387	$131.84	$131.85	$131.80
Purchase #5	$141.26	10.338%	$155.8635	$155.86	$155.85	$155.90
Purchase #6	$109.28	13.667%	$124.2153	$124.22	$124.20	$124.20
Purchase #7	$53.55	3.206%	$55.2668	$55.27	$55.25	$55.30
7 purchase totals =	$699.08		$756.5961	$756.60	$756.55	$756.60