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	$203.82	9.604%	$223.3949	$223.39	$223.40	$223.40
Purchase #2	$196.39	4.765%	$205.748	$205.75	$205.75	$205.70
Purchase #3	$119.77	11.182%	$133.1627	$133.16	$133.15	$133.20
Purchase #4	$231.64	3.383%	$239.4764	$239.48	$239.50	$239.50
Purchase #5	$37.31	5.748%	$39.4546	$39.45	$39.45	$39.50
Purchase #6	$127.48	7.468%	$137.0002	$137.00	$137.00	$137.00
Purchase #7	$66.97	6.527%	$71.3411	$71.34	$71.35	$71.30
7 purchase totals =	$983.38		$1,049.5779	$1,049.57	$1,049.60	$1,049.60