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	$104.52	4.702%	$109.4345	$109.43	$109.45	$109.40
Purchase #2	$225.67	7.445%	$242.4711	$242.47	$242.45	$242.50
Purchase #3	$110.65	11.172%	$123.0118	$123.01	$123.00	$123.00
Purchase #4	$124.57	4.492%	$130.1657	$130.17	$130.15	$130.20
Purchase #5	$227.93	12.422%	$256.2435	$256.24	$256.25	$256.20
Purchase #6	$173.48	11.503%	$193.4354	$193.44	$193.45	$193.40
Purchase #7	$215.59	4.660%	$225.6365	$225.64	$225.65	$225.60
7 purchase totals =	$1,182.41		$1,280.3985	$1,280.40	$1,280.40	$1,280.30