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	$142.30	13.242%	$161.1434	$161.14	$161.15	$161.10
Purchase #2	$93.50	10.657%	$103.4643	$103.46	$103.45	$103.50
Purchase #3	$166.68	13.247%	$188.7601	$188.76	$188.75	$188.80
Purchase #4	$51.65	11.335%	$57.5045	$57.50	$57.50	$57.50
Purchase #5	$82.42	4.706%	$86.2987	$86.30	$86.30	$86.30
Purchase #6	$29.82	11.509%	$33.252	$33.25	$33.25	$33.30
Purchase #7	$86.35	6.656%	$92.0975	$92.10	$92.10	$92.10
7 purchase totals =	$652.72		$722.5205	$722.51	$722.50	$722.60