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	$145.94	5.278%	$153.6427	$153.64	$153.65	$153.60
Purchase #2	$145.48	5.503%	$153.4858	$153.49	$153.50	$153.50
Purchase #3	$109.76	4.752%	$114.9758	$114.98	$115.00	$115.00
Purchase #4	$34.75	11.570%	$38.7706	$38.77	$38.75	$38.80
Purchase #5	$183.78	7.166%	$196.9497	$196.95	$196.95	$196.90
Purchase #6	$98.80	8.553%	$107.2504	$107.25	$107.25	$107.30
Purchase #7	$246.83	11.612%	$275.4919	$275.49	$275.50	$275.50
7 purchase totals =	$965.34		$1,040.5669	$1,040.57	$1,040.60	$1,040.60