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	$178.28	10.320%	$196.6785	$196.68	$196.70	$196.70
Purchase #2	$116.61	8.181%	$126.1499	$126.15	$126.15	$126.10
Purchase #3	$21.30	4.578%	$22.2751	$22.28	$22.30	$22.30
Purchase #4	$150.47	7.772%	$162.1645	$162.16	$162.15	$162.20
Purchase #5	$132.66	7.803%	$143.0115	$143.01	$143.00	$143.00
Purchase #6	$48.93	13.261%	$55.4186	$55.42	$55.40	$55.40
Purchase #7	$95.50	3.108%	$98.4681	$98.47	$98.45	$98.50
7 purchase totals =	$743.75		$804.1662	$804.17	$804.15	$804.20