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	$241.65	10.321%	$266.5907	$266.59	$266.60	$266.60
Purchase #2	$222.29	5.535%	$234.5938	$234.59	$234.60	$234.60
Purchase #3	$44.79	10.565%	$49.5221	$49.52	$49.50	$49.50
Purchase #4	$186.82	12.866%	$210.8563	$210.86	$210.85	$210.90
Purchase #5	$33.68	11.281%	$37.4794	$37.48	$37.50	$37.50
Purchase #6	$208.64	13.629%	$237.0755	$237.08	$237.10	$237.10
Purchase #7	$19.87	4.249%	$20.7143	$20.71	$20.70	$20.70
7 purchase totals =	$957.74		$1,056.8321	$1,056.83	$1,056.85	$1,056.90