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	$51.70	3.390%	$53.4526	$53.45	$53.45	$53.50
Purchase #2	$44.93	8.140%	$48.5873	$48.59	$48.60	$48.60
Purchase #3	$69.82	9.446%	$76.4152	$76.42	$76.40	$76.40
Purchase #4	$229.86	10.252%	$253.4252	$253.43	$253.45	$253.40
Purchase #5	$127.27	7.123%	$136.3354	$136.34	$136.35	$136.30
Purchase #6	$109.52	4.551%	$114.5043	$114.50	$114.50	$114.50
Purchase #7	$200.39	7.408%	$215.2349	$215.23	$215.25	$215.20
7 purchase totals =	$833.49		$897.9549	$897.96	$898.00	$897.90