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	$95.79	13.646%	$108.8615	$108.86	$108.85	$108.90
Purchase #2	$90.43	8.729%	$98.3236	$98.32	$98.30	$98.30
Purchase #3	$109.64	5.143%	$115.2788	$115.28	$115.30	$115.30
Purchase #4	$31.95	10.475%	$35.2968	$35.30	$35.30	$35.30
Purchase #5	$54.26	13.283%	$61.4674	$61.47	$61.45	$61.50
Purchase #6	$241.37	5.806%	$255.3839	$255.38	$255.40	$255.40
Purchase #7	$121.52	8.292%	$131.5964	$131.60	$131.60	$131.60
7 purchase totals =	$744.96		$806.2084	$806.21	$806.20	$806.30