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	$82.57	3.389%	$85.3683	$85.37	$85.35	$85.40
Purchase #2	$49.81	9.644%	$54.6137	$54.61	$54.60	$54.60
Purchase #3	$37.94	3.759%	$39.3662	$39.37	$39.35	$39.40
Purchase #4	$243.82	5.751%	$257.8421	$257.84	$257.85	$257.80
Purchase #5	$18.34	12.314%	$20.5984	$20.60	$20.60	$20.60
Purchase #6	$165.54	9.696%	$181.5908	$181.59	$181.60	$181.60
Purchase #7	$97.65	10.778%	$108.1747	$108.17	$108.15	$108.20
7 purchase totals =	$695.67		$747.5542	$747.55	$747.50	$747.60