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	$20.46	5.631%	$21.6121	$21.61	$21.60	$21.60
Purchase #2	$237.25	8.752%	$258.0141	$258.01	$258.00	$258.00
Purchase #3	$192.95	10.128%	$212.492	$212.49	$212.50	$212.50
Purchase #4	$22.45	7.251%	$24.0778	$24.08	$24.10	$24.10
Purchase #5	$51.43	4.351%	$53.6677	$53.67	$53.65	$53.70
Purchase #6	$112.64	9.718%	$123.5864	$123.59	$123.60	$123.60
Purchase #7	$30.70	4.175%	$31.9817	$31.98	$32.00	$32.00
7 purchase totals =	$667.88		$725.4318	$725.43	$725.45	$725.50