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	$183.43	7.313%	$196.8442	$196.84	$196.85	$196.80
Purchase #2	$74.67	12.199%	$83.779	$83.78	$83.80	$83.80
Purchase #3	$50.43	8.223%	$54.5769	$54.58	$54.60	$54.60
Purchase #4	$32.52	5.777%	$34.3987	$34.40	$34.40	$34.40
Purchase #5	$147.88	7.459%	$158.9104	$158.91	$158.90	$158.90
Purchase #6	$27.97	11.547%	$31.1997	$31.20	$31.20	$31.20
Purchase #7	$140.32	13.384%	$159.1004	$159.10	$159.10	$159.10
7 purchase totals =	$657.22		$718.8093	$718.81	$718.85	$718.80