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	$183.71	11.227%	$204.3351	$204.34	$204.35	$204.30
Purchase #2	$107.91	3.777%	$111.9858	$111.99	$112.00	$112.00
Purchase #3	$38.85	10.105%	$42.7758	$42.78	$42.80	$42.80
Purchase #4	$248.50	6.190%	$263.8822	$263.88	$263.90	$263.90
Purchase #5	$66.37	10.104%	$73.076	$73.08	$73.10	$73.10
Purchase #6	$41.68	10.505%	$46.0585	$46.06	$46.05	$46.10
Purchase #7	$196.36	13.233%	$222.3443	$222.34	$222.35	$222.30
7 purchase totals =	$883.38		$964.4577	$964.47	$964.55	$964.50