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	$56.34	6.381%	$59.9351	$59.94	$59.95	$59.90
Purchase #2	$208.90	6.554%	$222.5913	$222.59	$222.60	$222.60
Purchase #3	$178.87	4.601%	$187.0998	$187.10	$187.10	$187.10
Purchase #4	$135.40	5.471%	$142.8077	$142.81	$142.80	$142.80
Purchase #5	$40.80	12.824%	$46.0322	$46.03	$46.05	$46.00
Purchase #6	$136.76	7.451%	$146.95	$146.95	$146.95	$147.00
Purchase #7	$228.95	12.656%	$257.9259	$257.93	$257.95	$257.90
7 purchase totals =	$986.02		$1,063.3420	$1,063.35	$1,063.40	$1,063.30