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	$111.89	10.634%	$123.7884	$123.79	$123.80	$123.80
Purchase #2	$98.62	4.374%	$102.9336	$102.93	$102.95	$102.90
Purchase #3	$102.66	10.853%	$113.8017	$113.80	$113.80	$113.80
Purchase #4	$205.84	4.217%	$214.5203	$214.52	$214.50	$214.50
Purchase #5	$143.87	8.626%	$156.2802	$156.28	$156.30	$156.30
Purchase #6	$226.74	3.602%	$234.9072	$234.91	$234.90	$234.90
Purchase #7	$178.47	10.159%	$196.6008	$196.60	$196.60	$196.60
7 purchase totals =	$1,068.09		$1,142.8322	$1,142.83	$1,142.85	$1,142.80