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	$131.30	13.420%	$148.9205	$148.92	$148.90	$148.90
Purchase #2	$61.91	7.568%	$66.5953	$66.60	$66.60	$66.60
Purchase #3	$105.98	13.379%	$120.1591	$120.16	$120.15	$120.20
Purchase #4	$5.32	4.710%	$5.5706	$5.57	$5.55	$5.60
Purchase #5	$55.90	13.257%	$63.3107	$63.31	$63.30	$63.30
Purchase #6	$119.86	8.307%	$129.8168	$129.82	$129.80	$129.80
Purchase #7	$184.95	6.133%	$196.293	$196.29	$196.30	$196.30
7 purchase totals =	$665.22		$730.6660	$730.67	$730.60	$730.70