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	$198.84	6.108%	$210.9851	$210.99	$211.00	$211.00
Purchase #2	$127.27	3.157%	$131.2879	$131.29	$131.30	$131.30
Purchase #3	$246.26	3.762%	$255.5243	$255.52	$255.50	$255.50
Purchase #4	$130.90	4.866%	$137.2696	$137.27	$137.25	$137.30
Purchase #5	$108.76	5.422%	$114.657	$114.66	$114.65	$114.70
Purchase #6	$97.88	3.832%	$101.6308	$101.63	$101.65	$101.60
Purchase #7	$60.91	5.845%	$64.4702	$64.47	$64.45	$64.50
7 purchase totals =	$970.82		$1,015.8249	$1,015.83	$1,015.80	$1,015.90