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	$79.52	3.796%	$82.5386	$82.54	$82.55	$82.50
Purchase #2	$87.59	5.537%	$92.4399	$92.44	$92.45	$92.40
Purchase #3	$95.73	10.369%	$105.6562	$105.66	$105.65	$105.70
Purchase #4	$29.83	3.299%	$30.8141	$30.81	$30.80	$30.80
Purchase #5	$144.66	6.793%	$154.4868	$154.49	$154.50	$154.50
Purchase #6	$119.98	4.116%	$124.9184	$124.92	$124.90	$124.90
Purchase #7	$117.53	4.819%	$123.1938	$123.19	$123.20	$123.20
7 purchase totals =	$674.84		$714.0478	$714.05	$714.05	$714.00