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	$52.94	12.735%	$59.6819	$59.68	$59.70	$59.70
Purchase #2	$147.82	11.695%	$165.1075	$165.11	$165.10	$165.10
Purchase #3	$13.83	9.218%	$15.1048	$15.10	$15.10	$15.10
Purchase #4	$107.72	3.591%	$111.5882	$111.59	$111.60	$111.60
Purchase #5	$34.50	6.332%	$36.6845	$36.68	$36.70	$36.70
Purchase #6	$207.32	13.649%	$235.6171	$235.62	$235.60	$235.60
Purchase #7	$61.45	8.727%	$66.8127	$66.81	$66.80	$66.80
7 purchase totals =	$625.58		$690.5967	$690.59	$690.60	$690.60