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	$63.73	7.627%	$68.5907	$68.59	$68.60	$68.60
Purchase #2	$83.83	7.841%	$90.4031	$90.40	$90.40	$90.40
Purchase #3	$126.70	12.806%	$142.9252	$142.93	$142.95	$142.90
Purchase #4	$6.28	10.545%	$6.9422	$6.94	$6.95	$6.90
Purchase #5	$186.37	9.673%	$204.3976	$204.40	$204.40	$204.40
Purchase #6	$242.29	5.438%	$255.4657	$255.47	$255.45	$255.50
Purchase #7	$237.93	13.244%	$269.4414	$269.44	$269.45	$269.40
7 purchase totals =	$947.13		$1,038.1659	$1,038.17	$1,038.20	$1,038.10