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	$226.25	11.564%	$252.4136	$252.41	$252.40	$252.40
Purchase #2	$226.29	3.488%	$234.183	$234.18	$234.20	$234.20
Purchase #3	$245.32	12.233%	$275.33	$275.33	$275.35	$275.30
Purchase #4	$47.93	6.819%	$51.1983	$51.20	$51.20	$51.20
Purchase #5	$18.72	6.530%	$19.9424	$19.94	$19.95	$19.90
Purchase #6	$52.35	13.721%	$59.5329	$59.53	$59.55	$59.50
Purchase #7	$154.93	11.292%	$172.4247	$172.42	$172.40	$172.40
7 purchase totals =	$971.79		$1,065.0249	$1,065.01	$1,065.05	$1,064.90