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	$214.52	13.844%	$244.2181	$244.22	$244.20	$244.20
Purchase #2	$80.85	10.159%	$89.0636	$89.06	$89.05	$89.10
Purchase #3	$169.26	4.866%	$177.4962	$177.50	$177.50	$177.50
Purchase #4	$85.54	4.719%	$89.5766	$89.58	$89.60	$89.60
Purchase #5	$109.73	8.569%	$119.1328	$119.13	$119.15	$119.10
Purchase #6	$10.67	6.326%	$11.345	$11.35	$11.35	$11.30
Purchase #7	$21.50	9.206%	$23.4793	$23.48	$23.50	$23.50
7 purchase totals =	$692.07		$754.3116	$754.32	$754.35	$754.30