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	$232.52	7.774%	$250.5961	$250.60	$250.60	$250.60
Purchase #2	$16.64	4.735%	$17.4279	$17.43	$17.45	$17.40
Purchase #3	$224.86	11.803%	$251.4002	$251.40	$251.40	$251.40
Purchase #4	$138.69	3.478%	$143.5136	$143.51	$143.50	$143.50
Purchase #5	$105.25	4.350%	$109.8284	$109.83	$109.85	$109.80
Purchase #6	$125.59	12.689%	$141.5261	$141.53	$141.55	$141.50
Purchase #7	$136.58	6.238%	$145.0999	$145.10	$145.10	$145.10
7 purchase totals =	$980.13		$1,059.3922	$1,059.40	$1,059.45	$1,059.30