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	$66.55	12.226%	$74.6864	$74.69	$74.70	$74.70
Purchase #2	$13.62	12.378%	$15.3059	$15.31	$15.30	$15.30
Purchase #3	$73.40	12.336%	$82.4546	$82.45	$82.45	$82.50
Purchase #4	$153.26	12.553%	$172.4987	$172.50	$172.50	$172.50
Purchase #5	$108.25	10.521%	$119.639	$119.64	$119.65	$119.60
Purchase #6	$62.56	6.227%	$66.4556	$66.46	$66.45	$66.50
Purchase #7	$160.64	4.868%	$168.46	$168.46	$168.45	$168.50
7 purchase totals =	$638.28		$699.5002	$699.51	$699.50	$699.60