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	$233.75	8.440%	$253.4785	$253.48	$253.50	$253.50
Purchase #2	$229.80	5.716%	$242.9354	$242.94	$242.95	$242.90
Purchase #3	$229.83	8.143%	$248.5451	$248.55	$248.55	$248.50
Purchase #4	$57.89	8.611%	$62.8749	$62.87	$62.85	$62.90
Purchase #5	$101.66	4.600%	$106.3364	$106.34	$106.35	$106.30
Purchase #6	$66.47	12.738%	$74.9369	$74.94	$74.95	$74.90
Purchase #7	$70.49	11.311%	$78.4631	$78.46	$78.45	$78.50
7 purchase totals =	$989.89		$1,067.5703	$1,067.58	$1,067.60	$1,067.50