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	$89.64	9.779%	$98.4059	$98.41	$98.40	$98.40
Purchase #2	$233.83	8.373%	$253.4086	$253.41	$253.40	$253.40
Purchase #3	$180.48	8.831%	$196.4182	$196.42	$196.40	$196.40
Purchase #4	$209.92	10.577%	$232.1232	$232.12	$232.10	$232.10
Purchase #5	$215.94	13.466%	$245.0185	$245.02	$245.00	$245.00
Purchase #6	$66.51	9.488%	$72.8205	$72.82	$72.80	$72.80
Purchase #7	$35.74	7.660%	$38.4777	$38.48	$38.50	$38.50
7 purchase totals =	$1,032.06		$1,136.6726	$1,136.68	$1,136.60	$1,136.60