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	$222.57	11.604%	$248.397	$248.40	$248.40	$248.40
Purchase #2	$38.65	12.373%	$43.4322	$43.43	$43.45	$43.40
Purchase #3	$164.73	13.598%	$187.13	$187.13	$187.15	$187.10
Purchase #4	$245.31	8.708%	$266.6716	$266.67	$266.65	$266.70
Purchase #5	$126.35	10.451%	$139.5548	$139.55	$139.55	$139.60
Purchase #6	$211.27	8.340%	$228.8899	$228.89	$228.90	$228.90
Purchase #7	$52.88	3.818%	$54.899	$54.90	$54.90	$54.90
7 purchase totals =	$1,061.76		$1,168.9745	$1,168.97	$1,169.00	$1,169.00