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	$217.60	11.798%	$243.2724	$243.27	$243.25	$243.30
Purchase #2	$43.47	12.626%	$48.9585	$48.96	$48.95	$49.00
Purchase #3	$102.48	6.163%	$108.7958	$108.80	$108.80	$108.80
Purchase #4	$56.69	9.435%	$62.0387	$62.04	$62.05	$62.00
Purchase #5	$78.69	12.739%	$88.7143	$88.71	$88.70	$88.70
Purchase #6	$87.52	4.542%	$91.4952	$91.50	$91.50	$91.50
Purchase #7	$90.78	5.295%	$95.5868	$95.59	$95.60	$95.60
7 purchase totals =	$677.23		$738.8617	$738.87	$738.85	$738.90