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	$203.64	7.367%	$218.6422	$218.64	$218.65	$218.60
Purchase #2	$65.68	10.272%	$72.4266	$72.43	$72.45	$72.40
Purchase #3	$111.85	5.565%	$118.0745	$118.07	$118.05	$118.10
Purchase #4	$33.45	12.156%	$37.5162	$37.52	$37.50	$37.50
Purchase #5	$242.79	10.587%	$268.4942	$268.49	$268.50	$268.50
Purchase #6	$238.42	12.291%	$267.7242	$267.72	$267.70	$267.70
Purchase #7	$115.42	13.458%	$130.9532	$130.95	$130.95	$131.00
7 purchase totals =	$1,011.25		$1,113.8311	$1,113.82	$1,113.80	$1,113.80