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	$193.46	7.874%	$208.693	$208.69	$208.70	$208.70
Purchase #2	$229.93	12.643%	$259	$259.00	$259.00	$259.00
Purchase #3	$103.90	7.401%	$111.5896	$111.59	$111.60	$111.60
Purchase #4	$80.50	11.308%	$89.6029	$89.60	$89.60	$89.60
Purchase #5	$85.44	10.512%	$94.4215	$94.42	$94.40	$94.40
Purchase #6	$194.61	7.463%	$209.1337	$209.13	$209.15	$209.10
Purchase #7	$69.43	5.131%	$72.9925	$72.99	$73.00	$73.00
7 purchase totals =	$957.27		$1,045.4332	$1,045.42	$1,045.45	$1,045.40