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	$33.34	4.225%	$34.7486	$34.75	$34.75	$34.70
Purchase #2	$153.92	8.215%	$166.5645	$166.56	$166.55	$166.60
Purchase #3	$222.40	6.181%	$236.1465	$236.15	$236.15	$236.10
Purchase #4	$184.43	7.406%	$198.0889	$198.09	$198.10	$198.10
Purchase #5	$69.39	4.374%	$72.4251	$72.43	$72.45	$72.40
Purchase #6	$226.88	5.131%	$238.5212	$238.52	$238.50	$238.50
Purchase #7	$145.93	5.640%	$154.1605	$154.16	$154.15	$154.20
7 purchase totals =	$1,036.29		$1,100.6553	$1,100.66	$1,100.65	$1,100.60