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	$56.99	9.710%	$62.5237	$62.52	$62.50	$62.50
Purchase #2	$163.47	11.731%	$182.6467	$182.65	$182.65	$182.60
Purchase #3	$51.46	4.858%	$53.9599	$53.96	$53.95	$54.00
Purchase #4	$34.57	11.289%	$38.4726	$38.47	$38.45	$38.50
Purchase #5	$148.66	5.661%	$157.0756	$157.08	$157.10	$157.10
Purchase #6	$224.38	10.594%	$248.1508	$248.15	$248.15	$248.20
Purchase #7	$52.54	13.566%	$59.6676	$59.67	$59.65	$59.70
7 purchase totals =	$732.07		$802.4969	$802.50	$802.45	$802.60