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	$116.49	13.281%	$131.961	$131.96	$131.95	$132.00
Purchase #2	$124.94	10.820%	$138.4585	$138.46	$138.45	$138.50
Purchase #3	$228.46	13.304%	$258.8543	$258.85	$258.85	$258.90
Purchase #4	$197.28	3.161%	$203.516	$203.52	$203.50	$203.50
Purchase #5	$87.71	3.283%	$90.5895	$90.59	$90.60	$90.60
Purchase #6	$205.38	8.796%	$223.4452	$223.45	$223.45	$223.40
Purchase #7	$142.73	4.122%	$148.6133	$148.61	$148.60	$148.60
7 purchase totals =	$1,102.99		$1,195.4378	$1,195.44	$1,195.40	$1,195.50