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	$155.75	13.239%	$176.3697	$176.37	$176.35	$176.40
Purchase #2	$127.38	3.515%	$131.8574	$131.86	$131.85	$131.90
Purchase #3	$126.84	3.437%	$131.1995	$131.20	$131.20	$131.20
Purchase #4	$12.92	4.219%	$13.4651	$13.47	$13.45	$13.50
Purchase #5	$219.96	9.249%	$240.3041	$240.30	$240.30	$240.30
Purchase #6	$107.69	7.340%	$115.5944	$115.59	$115.60	$115.60
Purchase #7	$114.84	3.844%	$119.2544	$119.25	$119.25	$119.30
7 purchase totals =	$865.38		$928.0446	$928.04	$928.00	$928.20