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	$56.39	10.797%	$62.4784	$62.48	$62.50	$62.50
Purchase #2	$96.34	4.440%	$100.6175	$100.62	$100.60	$100.60
Purchase #3	$11.92	9.810%	$13.0894	$13.09	$13.10	$13.10
Purchase #4	$19.38	5.812%	$20.5064	$20.51	$20.50	$20.50
Purchase #5	$147.98	5.104%	$155.5329	$155.53	$155.55	$155.50
Purchase #6	$210.77	12.836%	$237.8244	$237.82	$237.80	$237.80
Purchase #7	$141.80	4.531%	$148.225	$148.23	$148.25	$148.20
7 purchase totals =	$684.58		$738.2740	$738.28	$738.30	$738.20