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	$233.69	10.810%	$258.9519	$258.95	$258.95	$259.00
Purchase #2	$142.92	10.793%	$158.3454	$158.35	$158.35	$158.30
Purchase #3	$118.64	8.293%	$128.4788	$128.48	$128.50	$128.50
Purchase #4	$111.82	6.814%	$119.4394	$119.44	$119.45	$119.40
Purchase #5	$154.28	3.374%	$159.4854	$159.49	$159.50	$159.50
Purchase #6	$61.27	9.499%	$67.09	$67.09	$67.10	$67.10
Purchase #7	$215.70	10.393%	$238.1177	$238.12	$238.10	$238.10
7 purchase totals =	$1,038.32		$1,129.9086	$1,129.92	$1,129.95	$1,129.90