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	$162.78	9.516%	$178.2701	$178.27	$178.25	$178.30
Purchase #2	$37.78	8.120%	$40.8477	$40.85	$40.85	$40.80
Purchase #3	$9.65	8.704%	$10.4899	$10.49	$10.50	$10.50
Purchase #4	$149.86	10.503%	$165.5998	$165.60	$165.60	$165.60
Purchase #5	$160.25	5.163%	$168.5237	$168.52	$168.50	$168.50
Purchase #6	$12.82	5.720%	$13.5533	$13.55	$13.55	$13.60
Purchase #7	$169.68	13.617%	$192.7853	$192.79	$192.80	$192.80
7 purchase totals =	$702.82		$770.0698	$770.07	$770.05	$770.10