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	$208.54	3.434%	$215.7013	$215.70	$215.70	$215.70
Purchase #2	$176.27	13.689%	$200.3996	$200.40	$200.40	$200.40
Purchase #3	$111.55	13.842%	$126.9908	$126.99	$127.00	$127.00
Purchase #4	$74.91	11.496%	$83.5217	$83.52	$83.50	$83.50
Purchase #5	$201.70	4.239%	$210.2501	$210.25	$210.25	$210.30
Purchase #6	$127.85	6.637%	$136.3354	$136.34	$136.35	$136.30
Purchase #7	$103.98	7.862%	$112.1549	$112.15	$112.15	$112.20
7 purchase totals =	$1,004.80		$1,085.3538	$1,085.35	$1,085.35	$1,085.40