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	$225.80	13.245%	$255.7072	$255.71	$255.70	$255.70
Purchase #2	$102.72	8.826%	$111.7861	$111.79	$111.80	$111.80
Purchase #3	$184.48	6.409%	$196.3033	$196.30	$196.30	$196.30
Purchase #4	$61.95	13.206%	$70.1311	$70.13	$70.15	$70.10
Purchase #5	$119.68	12.374%	$134.4892	$134.49	$134.50	$134.50
Purchase #6	$69.48	7.649%	$74.7945	$74.79	$74.80	$74.80
Purchase #7	$205.98	4.619%	$215.4942	$215.49	$215.50	$215.50
7 purchase totals =	$970.09		$1,058.7056	$1,058.70	$1,058.75	$1,058.70