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	$100.38	4.310%	$104.7064	$104.71	$104.70	$104.70
Purchase #2	$103.95	7.602%	$111.8523	$111.85	$111.85	$111.90
Purchase #3	$204.70	6.489%	$217.983	$217.98	$218.00	$218.00
Purchase #4	$38.50	5.500%	$40.6175	$40.62	$40.60	$40.60
Purchase #5	$142.87	10.448%	$157.7971	$157.80	$157.80	$157.80
Purchase #6	$205.41	8.458%	$222.7836	$222.78	$222.80	$222.80
Purchase #7	$224.58	7.218%	$240.7902	$240.79	$240.80	$240.80
7 purchase totals =	$1,020.39		$1,096.5301	$1,096.53	$1,096.55	$1,096.60