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	$143.26	11.325%	$159.4842	$159.48	$159.50	$159.50
Purchase #2	$236.43	5.564%	$249.585	$249.59	$249.60	$249.60
Purchase #3	$101.31	7.672%	$109.0825	$109.08	$109.10	$109.10
Purchase #4	$69.27	8.214%	$74.9598	$74.96	$74.95	$75.00
Purchase #5	$145.51	3.690%	$150.8793	$150.88	$150.90	$150.90
Purchase #6	$227.32	12.823%	$256.4692	$256.47	$256.45	$256.50
Purchase #7	$67.52	5.385%	$71.156	$71.16	$71.15	$71.20
7 purchase totals =	$990.62		$1,071.6160	$1,071.62	$1,071.65	$1,071.80