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	$103.30	7.612%	$111.1632	$111.16	$111.15	$111.20
Purchase #2	$139.37	4.382%	$145.4772	$145.48	$145.50	$145.50
Purchase #3	$106.53	7.277%	$114.2822	$114.28	$114.30	$114.30
Purchase #4	$63.63	11.506%	$70.9513	$70.95	$70.95	$71.00
Purchase #5	$9.57	9.775%	$10.5055	$10.51	$10.50	$10.50
Purchase #6	$213.63	3.395%	$220.8827	$220.88	$220.90	$220.90
Purchase #7	$38.40	5.295%	$40.4333	$40.43	$40.45	$40.40
7 purchase totals =	$674.43		$713.6954	$713.69	$713.75	$713.80