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	$52.62	13.265%	$59.6	$59.60	$59.60	$59.60
Purchase #2	$16.96	10.779%	$18.7881	$18.79	$18.80	$18.80
Purchase #3	$89.31	6.128%	$94.7829	$94.78	$94.80	$94.80
Purchase #4	$31.26	3.416%	$32.3278	$32.33	$32.35	$32.30
Purchase #5	$89.49	10.315%	$98.7209	$98.72	$98.70	$98.70
Purchase #6	$115.57	7.685%	$124.4516	$124.45	$124.45	$124.50
Purchase #7	$44.31	10.596%	$49.0051	$49.01	$49.00	$49.00
7 purchase totals =	$439.52		$477.6764	$477.68	$477.70	$477.70