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	$162.92	12.442%	$183.1905	$183.19	$183.20	$183.20
Purchase #2	$143.70	10.122%	$158.2453	$158.25	$158.25	$158.20
Purchase #3	$164.60	13.194%	$186.3173	$186.32	$186.30	$186.30
Purchase #4	$122.46	12.171%	$137.3646	$137.36	$137.35	$137.40
Purchase #5	$58.71	13.516%	$66.6452	$66.65	$66.65	$66.60
Purchase #6	$210.45	8.509%	$228.3572	$228.36	$228.35	$228.40
Purchase #7	$54.27	8.716%	$59.0002	$59.00	$59.00	$59.00
7 purchase totals =	$917.11		$1,019.1203	$1,019.13	$1,019.10	$1,019.10