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	$68.69	5.344%	$72.3608	$72.36	$72.35	$72.40
Purchase #2	$187.30	11.109%	$208.1072	$208.11	$208.10	$208.10
Purchase #3	$141.50	13.606%	$160.7525	$160.75	$160.75	$160.80
Purchase #4	$231.50	10.833%	$256.5784	$256.58	$256.60	$256.60
Purchase #5	$231.45	13.504%	$262.705	$262.71	$262.70	$262.70
Purchase #6	$82.93	13.609%	$94.2159	$94.22	$94.20	$94.20
Purchase #7	$106.72	10.643%	$118.0782	$118.08	$118.10	$118.10
7 purchase totals =	$1,050.09		$1,172.7980	$1,172.81	$1,172.80	$1,172.90