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	$212.64	13.810%	$242.0056	$242.01	$242.00	$242.00
Purchase #2	$177.33	4.419%	$185.1662	$185.17	$185.15	$185.20
Purchase #3	$9.52	9.609%	$10.4348	$10.43	$10.45	$10.40
Purchase #4	$16.42	4.536%	$17.1648	$17.16	$17.15	$17.20
Purchase #5	$147.48	11.751%	$164.8104	$164.81	$164.80	$164.80
Purchase #6	$18.52	9.407%	$20.2622	$20.26	$20.25	$20.30
Purchase #7	$42.56	6.643%	$45.3873	$45.39	$45.40	$45.40
7 purchase totals =	$624.47		$685.2313	$685.23	$685.20	$685.30