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	$214.98	9.569%	$235.5514	$235.55	$235.55	$235.60
Purchase #2	$210.72	6.724%	$224.8888	$224.89	$224.90	$224.90
Purchase #3	$100.31	8.125%	$108.4602	$108.46	$108.45	$108.50
Purchase #4	$119.50	7.148%	$128.0419	$128.04	$128.05	$128.00
Purchase #5	$148.42	4.838%	$155.6006	$155.60	$155.60	$155.60
Purchase #6	$83.55	7.237%	$89.5965	$89.60	$89.60	$89.60
Purchase #7	$34.56	4.703%	$36.1854	$36.19	$36.20	$36.20
7 purchase totals =	$912.04		$978.3248	$978.33	$978.35	$978.40