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	$239.60	11.377%	$266.8593	$266.86	$266.85	$266.90
Purchase #2	$238.48	5.165%	$250.7975	$250.80	$250.80	$250.80
Purchase #3	$116.81	12.264%	$131.1356	$131.14	$131.15	$131.10
Purchase #4	$174.37	6.592%	$185.8645	$185.86	$185.85	$185.90
Purchase #5	$110.97	9.273%	$121.2602	$121.26	$121.25	$121.30
Purchase #6	$28.34	13.245%	$32.0936	$32.09	$32.10	$32.10
Purchase #7	$43.60	7.389%	$46.8216	$46.82	$46.80	$46.80
7 purchase totals =	$952.17		$1,034.8323	$1,034.83	$1,034.80	$1,034.90