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	$157.87	6.301%	$167.8174	$167.82	$167.80	$167.80
Purchase #2	$19.95	13.381%	$22.6195	$22.62	$22.60	$22.60
Purchase #3	$131.43	9.277%	$143.6228	$143.62	$143.60	$143.60
Purchase #4	$54.89	4.669%	$57.4528	$57.45	$57.45	$57.50
Purchase #5	$178.29	12.581%	$200.7207	$200.72	$200.70	$200.70
Purchase #6	$151.98	10.517%	$167.9637	$167.96	$167.95	$168.00
Purchase #7	$102.27	13.256%	$115.8269	$115.83	$115.85	$115.80
7 purchase totals =	$796.68		$876.0238	$876.02	$875.95	$876.00