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	$50.72	5.856%	$53.6902	$53.69	$53.70	$53.70
Purchase #2	$145.52	10.256%	$160.4445	$160.44	$160.45	$160.40
Purchase #3	$214.90	11.213%	$238.9967	$239.00	$239.00	$239.00
Purchase #4	$249.60	13.273%	$282.7294	$282.73	$282.75	$282.70
Purchase #5	$52.62	6.153%	$55.8577	$55.86	$55.85	$55.90
Purchase #6	$38.93	9.668%	$42.6938	$42.69	$42.70	$42.70
Purchase #7	$180.30	5.423%	$190.0777	$190.08	$190.10	$190.10
7 purchase totals =	$932.59		$1,024.4900	$1,024.49	$1,024.55	$1,024.50