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	$241.59	5.761%	$255.508	$255.51	$255.50	$255.50
Purchase #2	$226.42	8.272%	$245.1495	$245.15	$245.15	$245.10
Purchase #3	$113.96	9.241%	$124.491	$124.49	$124.50	$124.50
Purchase #4	$119.31	10.305%	$131.6049	$131.60	$131.60	$131.60
Purchase #5	$103.56	4.604%	$108.3279	$108.33	$108.35	$108.30
Purchase #6	$129.86	11.720%	$145.0796	$145.08	$145.10	$145.10
Purchase #7	$48.36	11.726%	$54.0307	$54.03	$54.05	$54.00
7 purchase totals =	$983.06		$1,064.1916	$1,064.19	$1,064.25	$1,064.10