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	$40.35	10.318%	$44.5133	$44.51	$44.50	$44.50
Purchase #2	$151.98	10.819%	$168.4227	$168.42	$168.40	$168.40
Purchase #3	$152.46	5.242%	$160.452	$160.45	$160.45	$160.50
Purchase #4	$37.89	7.767%	$40.8329	$40.83	$40.85	$40.80
Purchase #5	$89.51	9.344%	$97.8738	$97.87	$97.85	$97.90
Purchase #6	$97.87	3.232%	$101.0332	$101.03	$101.05	$101.00
Purchase #7	$93.93	12.123%	$105.3171	$105.32	$105.30	$105.30
7 purchase totals =	$663.99		$718.4450	$718.43	$718.40	$718.40