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	$162.45	10.555%	$179.5966	$179.60	$179.60	$179.60
Purchase #2	$176.53	12.652%	$198.8646	$198.86	$198.85	$198.90
Purchase #3	$213.86	4.211%	$222.8656	$222.87	$222.85	$222.90
Purchase #4	$17.82	7.841%	$19.2173	$19.22	$19.20	$19.20
Purchase #5	$112.92	13.485%	$128.1473	$128.15	$128.15	$128.10
Purchase #6	$99.42	10.759%	$110.1166	$110.12	$110.10	$110.10
Purchase #7	$187.52	12.246%	$210.4837	$210.48	$210.50	$210.50
7 purchase totals =	$970.52		$1,069.2917	$1,069.30	$1,069.25	$1,069.30