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	$139.45	6.426%	$148.4111	$148.41	$148.40	$148.40
Purchase #2	$153.63	5.716%	$162.4115	$162.41	$162.40	$162.40
Purchase #3	$184.29	7.316%	$197.7727	$197.77	$197.75	$197.80
Purchase #4	$132.61	13.546%	$150.5734	$150.57	$150.55	$150.60
Purchase #5	$97.28	3.176%	$100.3696	$100.37	$100.35	$100.40
Purchase #6	$94.65	6.514%	$100.8155	$100.82	$100.80	$100.80
Purchase #7	$141.28	5.186%	$148.6068	$148.61	$148.60	$148.60
7 purchase totals =	$943.19		$1,008.9606	$1,008.96	$1,008.85	$1,009.00