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	$247.82	10.822%	$274.6391	$274.64	$274.65	$274.60
Purchase #2	$100.61	5.723%	$106.3679	$106.37	$106.35	$106.40
Purchase #3	$18.59	7.721%	$20.0253	$20.03	$20.05	$20.00
Purchase #4	$74.67	10.225%	$82.305	$82.31	$82.30	$82.30
Purchase #5	$207.39	7.455%	$222.8509	$222.85	$222.85	$222.90
Purchase #6	$17.60	7.240%	$18.8742	$18.87	$18.85	$18.90
Purchase #7	$43.61	8.264%	$47.2139	$47.21	$47.20	$47.20
7 purchase totals =	$710.29		$772.2763	$772.28	$772.25	$772.30