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	$63.77	4.279%	$66.4987	$66.50	$66.50	$66.50
Purchase #2	$215.39	6.656%	$229.7264	$229.73	$229.75	$229.70
Purchase #3	$241.59	8.810%	$262.8741	$262.87	$262.85	$262.90
Purchase #4	$238.56	10.318%	$263.1746	$263.17	$263.15	$263.20
Purchase #5	$231.60	11.690%	$258.674	$258.67	$258.65	$258.70
Purchase #6	$229.52	12.603%	$258.4464	$258.45	$258.45	$258.40
Purchase #7	$63.57	11.361%	$70.7922	$70.79	$70.80	$70.80
7 purchase totals =	$1,284.00		$1,410.1864	$1,410.18	$1,410.15	$1,410.20