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	$161.83	4.310%	$168.8049	$168.80	$168.80	$168.80
Purchase #2	$195.50	6.393%	$207.9983	$208.00	$208.00	$208.00
Purchase #3	$20.28	6.569%	$21.6122	$21.61	$21.60	$21.60
Purchase #4	$245.66	10.867%	$272.3559	$272.36	$272.35	$272.40
Purchase #5	$233.95	6.313%	$248.7193	$248.72	$248.70	$248.70
Purchase #6	$73.77	13.667%	$83.8521	$83.85	$83.85	$83.90
Purchase #7	$108.81	13.289%	$123.2698	$123.27	$123.25	$123.30
7 purchase totals =	$1,039.80		$1,126.6125	$1,126.61	$1,126.55	$1,126.70