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	$38.50	7.663%	$41.4503	$41.45	$41.45	$41.50
Purchase #2	$86.69	4.577%	$90.6578	$90.66	$90.65	$90.70
Purchase #3	$23.53	5.500%	$24.8242	$24.82	$24.80	$24.80
Purchase #4	$173.66	4.663%	$181.7578	$181.76	$181.75	$181.80
Purchase #5	$76.25	9.249%	$83.3024	$83.30	$83.30	$83.30
Purchase #6	$213.68	5.287%	$224.9773	$224.98	$225.00	$225.00
Purchase #7	$31.73	10.771%	$35.1476	$35.15	$35.15	$35.10
7 purchase totals =	$644.04		$682.1174	$682.12	$682.10	$682.20