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	$217.79	12.439%	$244.8809	$244.88	$244.90	$244.90
Purchase #2	$42.71	11.270%	$47.5234	$47.52	$47.50	$47.50
Purchase #3	$217.54	12.294%	$244.2844	$244.28	$244.30	$244.30
Purchase #4	$126.31	4.246%	$131.6731	$131.67	$131.65	$131.70
Purchase #5	$81.65	5.139%	$85.846	$85.85	$85.85	$85.80
Purchase #6	$118.89	11.784%	$132.9	$132.90	$132.90	$132.90
Purchase #7	$237.83	7.607%	$255.9217	$255.92	$255.90	$255.90
7 purchase totals =	$1,042.72		$1,143.0295	$1,143.02	$1,143.00	$1,143.00