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	$100.55	13.404%	$114.0277	$114.03	$114.05	$114.00
Purchase #2	$151.41	4.734%	$158.5777	$158.58	$158.60	$158.60
Purchase #3	$63.66	11.269%	$70.8338	$70.83	$70.85	$70.80
Purchase #4	$38.61	9.453%	$42.2598	$42.26	$42.25	$42.30
Purchase #5	$162.52	3.581%	$168.3398	$168.34	$168.35	$168.30
Purchase #6	$44.46	13.601%	$50.507	$50.51	$50.50	$50.50
Purchase #7	$230.29	10.554%	$254.5948	$254.59	$254.60	$254.60
7 purchase totals =	$791.50		$859.1406	$859.14	$859.20	$859.10