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	$78.30	10.291%	$86.3579	$86.36	$86.35	$86.40
Purchase #2	$165.35	10.364%	$182.4869	$182.49	$182.50	$182.50
Purchase #3	$62.75	12.491%	$70.5881	$70.59	$70.60	$70.60
Purchase #4	$70.75	8.702%	$76.9067	$76.91	$76.90	$76.90
Purchase #5	$36.66	4.707%	$38.3856	$38.39	$38.40	$38.40
Purchase #6	$116.86	9.859%	$128.3812	$128.38	$128.40	$128.40
Purchase #7	$204.54	8.832%	$222.605	$222.61	$222.60	$222.60
7 purchase totals =	$735.21		$805.7114	$805.73	$805.75	$805.80