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	$130.89	9.146%	$142.8612	$142.86	$142.85	$142.90
Purchase #2	$165.77	13.358%	$187.9136	$187.91	$187.90	$187.90
Purchase #3	$26.86	11.621%	$29.9814	$29.98	$30.00	$30.00
Purchase #4	$112.84	3.402%	$116.6788	$116.68	$116.70	$116.70
Purchase #5	$88.32	8.255%	$95.6108	$95.61	$95.60	$95.60
Purchase #6	$39.64	12.174%	$44.4658	$44.47	$44.45	$44.50
Purchase #7	$86.59	4.599%	$90.5723	$90.57	$90.55	$90.60
7 purchase totals =	$650.91		$708.0839	$708.08	$708.05	$708.20