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	$102.85	8.208%	$111.2919	$111.29	$111.30	$111.30
Purchase #2	$169.79	9.213%	$185.4328	$185.43	$185.45	$185.40
Purchase #3	$148.25	8.673%	$161.1077	$161.11	$161.10	$161.10
Purchase #4	$117.60	12.457%	$132.2494	$132.25	$132.25	$132.20
Purchase #5	$109.85	6.499%	$116.9892	$116.99	$117.00	$117.00
Purchase #6	$142.67	9.779%	$156.6217	$156.62	$156.60	$156.60
Purchase #7	$129.53	11.266%	$144.1228	$144.12	$144.10	$144.10
7 purchase totals =	$920.54		$1,007.8155	$1,007.81	$1,007.80	$1,007.70