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	$12.92	11.203%	$14.3674	$14.37	$14.35	$14.40
Purchase #2	$102.64	11.771%	$114.7218	$114.72	$114.70	$114.70
Purchase #3	$173.57	5.736%	$183.526	$183.53	$183.55	$183.50
Purchase #4	$6.95	5.336%	$7.3209	$7.32	$7.30	$7.30
Purchase #5	$185.25	12.644%	$208.673	$208.67	$208.65	$208.70
Purchase #6	$19.85	6.495%	$21.1393	$21.14	$21.15	$21.10
Purchase #7	$38.32	10.824%	$42.4678	$42.47	$42.45	$42.50
7 purchase totals =	$539.50		$592.2162	$592.22	$592.15	$592.20