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	$119.68	12.396%	$134.5155	$134.52	$134.50	$134.50
Purchase #2	$247.94	8.259%	$268.4174	$268.42	$268.40	$268.40
Purchase #3	$67.49	7.737%	$72.7117	$72.71	$72.70	$72.70
Purchase #4	$238.88	4.851%	$250.4681	$250.47	$250.45	$250.50
Purchase #5	$61.40	6.405%	$65.3327	$65.33	$65.35	$65.30
Purchase #6	$228.62	4.822%	$239.6441	$239.64	$239.65	$239.60
Purchase #7	$111.31	6.660%	$118.7232	$118.72	$118.70	$118.70
7 purchase totals =	$1,075.32		$1,149.8127	$1,149.81	$1,149.75	$1,149.70