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	$119.40	12.577%	$134.4169	$134.42	$134.40	$134.40
Purchase #2	$139.78	10.275%	$154.1424	$154.14	$154.15	$154.10
Purchase #3	$95.78	8.356%	$103.7834	$103.78	$103.80	$103.80
Purchase #4	$58.74	6.526%	$62.5734	$62.57	$62.55	$62.60
Purchase #5	$10.27	12.579%	$11.5619	$11.56	$11.55	$11.60
Purchase #6	$205.95	13.388%	$233.5226	$233.52	$233.50	$233.50
Purchase #7	$168.61	7.691%	$181.5778	$181.58	$181.60	$181.60
7 purchase totals =	$798.53		$881.5784	$881.57	$881.55	$881.60