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	$232.57	11.455%	$259.2109	$259.21	$259.20	$259.20
Purchase #2	$141.94	4.515%	$148.3486	$148.35	$148.35	$148.30
Purchase #3	$168.94	8.616%	$183.4959	$183.50	$183.50	$183.50
Purchase #4	$190.30	13.585%	$216.1523	$216.15	$216.15	$216.20
Purchase #5	$119.45	12.517%	$134.4016	$134.40	$134.40	$134.40
Purchase #6	$117.52	5.152%	$123.5746	$123.57	$123.55	$123.60
Purchase #7	$56.32	11.335%	$62.7039	$62.70	$62.70	$62.70
7 purchase totals =	$1,027.04		$1,127.8878	$1,127.88	$1,127.85	$1,127.90