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	$214.40	6.660%	$228.679	$228.68	$228.70	$228.70
Purchase #2	$95.42	3.309%	$98.5774	$98.58	$98.60	$98.60
Purchase #3	$108.95	3.565%	$112.8341	$112.83	$112.85	$112.80
Purchase #4	$17.89	7.816%	$19.2883	$19.29	$19.30	$19.30
Purchase #5	$93.30	7.642%	$100.43	$100.43	$100.45	$100.40
Purchase #6	$241.32	9.529%	$264.3154	$264.32	$264.30	$264.30
Purchase #7	$18.66	6.145%	$19.8067	$19.81	$19.80	$19.80
7 purchase totals =	$789.94		$843.9309	$843.94	$844.00	$843.90