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	$116.97	8.390%	$126.7838	$126.78	$126.80	$126.80
Purchase #2	$49.77	6.375%	$52.9428	$52.94	$52.95	$52.90
Purchase #3	$185.25	8.474%	$200.9481	$200.95	$200.95	$200.90
Purchase #4	$194.55	8.324%	$210.7443	$210.74	$210.75	$210.70
Purchase #5	$104.73	6.669%	$111.7144	$111.71	$111.70	$111.70
Purchase #6	$88.39	13.309%	$100.1538	$100.15	$100.15	$100.20
Purchase #7	$241.73	12.670%	$272.3572	$272.36	$272.35	$272.40
7 purchase totals =	$981.39		$1,075.6444	$1,075.63	$1,075.65	$1,075.60