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	$200.95	13.205%	$227.4854	$227.49	$227.50	$227.50
Purchase #2	$217.28	12.687%	$244.8463	$244.85	$244.85	$244.80
Purchase #3	$126.90	8.646%	$137.8718	$137.87	$137.85	$137.90
Purchase #4	$175.25	3.778%	$181.8709	$181.87	$181.85	$181.90
Purchase #5	$44.91	10.735%	$49.7311	$49.73	$49.75	$49.70
Purchase #6	$130.38	10.122%	$143.5771	$143.58	$143.60	$143.60
Purchase #7	$75.56	9.621%	$82.8296	$82.83	$82.85	$82.80
7 purchase totals =	$971.23		$1,068.2122	$1,068.22	$1,068.25	$1,068.20