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	$61.44	10.169%	$67.6878	$67.69	$67.70	$67.70
Purchase #2	$178.31	10.212%	$196.519	$196.52	$196.50	$196.50
Purchase #3	$110.62	12.382%	$124.317	$124.32	$124.30	$124.30
Purchase #4	$155.93	4.501%	$162.9484	$162.95	$162.95	$162.90
Purchase #5	$12.53	6.288%	$13.3179	$13.32	$13.30	$13.30
Purchase #6	$212.95	10.178%	$234.6241	$234.62	$234.60	$234.60
Purchase #7	$111.55	4.103%	$116.1269	$116.13	$116.15	$116.10
7 purchase totals =	$843.33		$915.5411	$915.55	$915.50	$915.40