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	$46.90	11.509%	$52.2977	$52.30	$52.30	$52.30
Purchase #2	$210.69	6.273%	$223.9066	$223.91	$223.90	$223.90
Purchase #3	$111.32	4.602%	$116.4429	$116.44	$116.45	$116.40
Purchase #4	$247.82	3.648%	$256.8605	$256.86	$256.85	$256.90
Purchase #5	$210.85	9.318%	$230.497	$230.50	$230.50	$230.50
Purchase #6	$44.59	13.758%	$50.7247	$50.72	$50.70	$50.70
Purchase #7	$182.25	13.789%	$207.3805	$207.38	$207.40	$207.40
7 purchase totals =	$1,054.42		$1,138.1099	$1,138.11	$1,138.10	$1,138.10