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	$196.31	10.327%	$216.5829	$216.58	$216.60	$216.60
Purchase #2	$29.77	10.407%	$32.8682	$32.87	$32.85	$32.90
Purchase #3	$93.47	12.836%	$105.4678	$105.47	$105.45	$105.50
Purchase #4	$147.28	9.452%	$161.2009	$161.20	$161.20	$161.20
Purchase #5	$75.78	3.657%	$78.5513	$78.55	$78.55	$78.60
Purchase #6	$9.77	10.143%	$10.761	$10.76	$10.75	$10.80
Purchase #7	$90.98	13.531%	$103.2905	$103.29	$103.30	$103.30
7 purchase totals =	$643.36		$708.7226	$708.72	$708.70	$708.90