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	$100.29	11.242%	$111.5646	$111.56	$111.55	$111.60
Purchase #2	$19.72	8.650%	$21.4258	$21.43	$21.45	$21.40
Purchase #3	$75.37	10.518%	$83.2974	$83.30	$83.30	$83.30
Purchase #4	$171.65	9.291%	$187.598	$187.60	$187.60	$187.60
Purchase #5	$203.59	6.791%	$217.4158	$217.42	$217.40	$217.40
Purchase #6	$49.31	12.146%	$55.2992	$55.30	$55.30	$55.30
Purchase #7	$65.70	5.827%	$69.5283	$69.53	$69.55	$69.50
7 purchase totals =	$685.63		$746.1291	$746.14	$746.15	$746.10