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	$104.57	9.824%	$114.843	$114.84	$114.85	$114.80
Purchase #2	$226.98	11.346%	$252.7332	$252.73	$252.75	$252.70
Purchase #3	$98.81	8.509%	$107.2177	$107.22	$107.20	$107.20
Purchase #4	$88.72	12.152%	$99.5013	$99.50	$99.50	$99.50
Purchase #5	$229.80	11.189%	$255.5123	$255.51	$255.50	$255.50
Purchase #6	$87.84	13.573%	$99.7625	$99.76	$99.75	$99.80
Purchase #7	$81.58	6.307%	$86.7253	$86.73	$86.75	$86.70
7 purchase totals =	$918.30		$1,016.2953	$1,016.29	$1,016.30	$1,016.20