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	$63.80	13.481%	$72.4009	$72.40	$72.40	$72.40
Purchase #2	$87.71	10.330%	$96.7704	$96.77	$96.75	$96.80
Purchase #3	$95.54	8.448%	$103.6112	$103.61	$103.60	$103.60
Purchase #4	$167.69	12.538%	$188.715	$188.72	$188.70	$188.70
Purchase #5	$62.87	5.418%	$66.2763	$66.28	$66.30	$66.30
Purchase #6	$16.83	9.485%	$18.4263	$18.43	$18.45	$18.40
Purchase #7	$140.50	12.295%	$157.7745	$157.77	$157.75	$157.80
7 purchase totals =	$634.94		$703.9746	$703.98	$703.95	$704.00