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	$104.27	11.583%	$116.3476	$116.35	$116.35	$116.30
Purchase #2	$238.47	12.103%	$267.332	$267.33	$267.35	$267.30
Purchase #3	$66.51	9.312%	$72.7034	$72.70	$72.70	$72.70
Purchase #4	$103.40	8.143%	$111.8199	$111.82	$111.80	$111.80
Purchase #5	$244.56	11.360%	$272.342	$272.34	$272.35	$272.30
Purchase #6	$245.98	6.700%	$262.4607	$262.46	$262.45	$262.50
Purchase #7	$167.71	13.776%	$190.8137	$190.81	$190.80	$190.80
7 purchase totals =	$1,170.90		$1,293.8193	$1,293.81	$1,293.80	$1,293.70