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	$9.62	9.528%	$10.5366	$10.54	$10.55	$10.50
Purchase #2	$15.46	7.386%	$16.6019	$16.60	$16.60	$16.60
Purchase #3	$183.59	11.287%	$204.3118	$204.31	$204.30	$204.30
Purchase #4	$174.66	6.414%	$185.8627	$185.86	$185.85	$185.90
Purchase #5	$64.97	11.477%	$72.4266	$72.43	$72.45	$72.40
Purchase #6	$158.33	3.630%	$164.0774	$164.08	$164.10	$164.10
Purchase #7	$250.75	11.504%	$279.5963	$279.60	$279.60	$279.60
7 purchase totals =	$857.38		$933.4133	$933.42	$933.45	$933.40