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	$84.30	6.309%	$89.6185	$89.62	$89.60	$89.60
Purchase #2	$66.78	6.134%	$70.8763	$70.88	$70.90	$70.90
Purchase #3	$137.81	13.567%	$156.5067	$156.51	$156.50	$156.50
Purchase #4	$5.58	9.749%	$6.124	$6.12	$6.10	$6.10
Purchase #5	$100.85	5.636%	$106.5339	$106.53	$106.55	$106.50
Purchase #6	$112.27	12.836%	$126.681	$126.68	$126.70	$126.70
Purchase #7	$176.59	12.256%	$198.2329	$198.23	$198.25	$198.20
7 purchase totals =	$684.18		$754.5733	$754.57	$754.60	$754.50