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	$126.92	12.610%	$142.9246	$142.92	$142.90	$142.90
Purchase #2	$104.66	6.465%	$111.4263	$111.43	$111.45	$111.40
Purchase #3	$121.56	7.660%	$130.8715	$130.87	$130.85	$130.90
Purchase #4	$153.72	4.151%	$160.1009	$160.10	$160.10	$160.10
Purchase #5	$18.82	3.606%	$19.4986	$19.50	$19.50	$19.50
Purchase #6	$227.26	3.239%	$234.621	$234.62	$234.60	$234.60
Purchase #7	$223.25	8.750%	$242.7844	$242.78	$242.80	$242.80
7 purchase totals =	$976.19		$1,042.2273	$1,042.22	$1,042.20	$1,042.20