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	$182.82	12.730%	$206.093	$206.09	$206.10	$206.10
Purchase #2	$49.30	10.115%	$54.2867	$54.29	$54.30	$54.30
Purchase #3	$160.28	13.438%	$181.8184	$181.82	$181.80	$181.80
Purchase #4	$114.43	3.397%	$118.3172	$118.32	$118.30	$118.30
Purchase #5	$161.58	7.376%	$173.4981	$173.50	$173.50	$173.50
Purchase #6	$85.92	6.612%	$91.601	$91.60	$91.60	$91.60
Purchase #7	$217.71	7.283%	$233.5658	$233.57	$233.55	$233.60
7 purchase totals =	$972.04		$1,059.1802	$1,059.19	$1,059.15	$1,059.20