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	$182.60	12.291%	$205.0434	$205.04	$205.05	$205.00
Purchase #2	$207.91	3.443%	$215.0683	$215.07	$215.05	$215.10
Purchase #3	$75.32	9.835%	$82.7277	$82.73	$82.75	$82.70
Purchase #4	$192.94	10.577%	$213.3473	$213.35	$213.35	$213.30
Purchase #5	$72.38	8.644%	$78.6365	$78.64	$78.65	$78.60
Purchase #6	$103.73	10.697%	$114.826	$114.83	$114.85	$114.80
Purchase #7	$229.70	11.295%	$255.6446	$255.64	$255.65	$255.60
7 purchase totals =	$1,064.58		$1,165.2938	$1,165.30	$1,165.35	$1,165.10