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	$15.63	12.557%	$17.5927	$17.59	$17.60	$17.60
Purchase #2	$105.68	3.683%	$109.5722	$109.57	$109.55	$109.60
Purchase #3	$85.42	5.294%	$89.9421	$89.94	$89.95	$89.90
Purchase #4	$75.92	8.734%	$82.5509	$82.55	$82.55	$82.60
Purchase #5	$115.32	6.191%	$122.4595	$122.46	$122.45	$122.50
Purchase #6	$234.52	10.466%	$259.0649	$259.06	$259.05	$259.10
Purchase #7	$76.76	5.783%	$81.199	$81.20	$81.20	$81.20
7 purchase totals =	$709.25		$762.3813	$762.37	$762.35	$762.50