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	$176.64	4.457%	$184.5128	$184.51	$184.50	$184.50
Purchase #2	$103.38	11.722%	$115.4982	$115.50	$115.50	$115.50
Purchase #3	$100.39	11.176%	$111.6096	$111.61	$111.60	$111.60
Purchase #4	$48.81	13.776%	$55.5341	$55.53	$55.55	$55.50
Purchase #5	$232.88	3.249%	$240.4463	$240.45	$240.45	$240.40
Purchase #6	$86.57	5.697%	$91.5019	$91.50	$91.50	$91.50
Purchase #7	$215.84	8.376%	$233.9188	$233.92	$233.90	$233.90
7 purchase totals =	$964.51		$1,033.0217	$1,033.02	$1,033.00	$1,032.90