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	$92.83	13.615%	$105.4688	$105.47	$105.45	$105.50
Purchase #2	$128.55	4.719%	$134.6163	$134.62	$134.60	$134.60
Purchase #3	$226.80	9.583%	$248.5342	$248.53	$248.55	$248.50
Purchase #4	$44.89	8.264%	$48.5997	$48.60	$48.60	$48.60
Purchase #5	$61.69	8.393%	$66.8676	$66.87	$66.85	$66.90
Purchase #6	$82.47	9.854%	$90.5966	$90.60	$90.60	$90.60
Purchase #7	$114.45	13.218%	$129.578	$129.58	$129.60	$129.60
7 purchase totals =	$751.68		$824.2612	$824.27	$824.25	$824.30