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	$191.48	9.238%	$209.1689	$209.17	$209.15	$209.20
Purchase #2	$139.86	13.541%	$158.7984	$158.80	$158.80	$158.80
Purchase #3	$71.34	10.553%	$78.8685	$78.87	$78.85	$78.90
Purchase #4	$46.68	9.131%	$50.9424	$50.94	$50.95	$50.90
Purchase #5	$62.93	6.514%	$67.0293	$67.03	$67.05	$67.00
Purchase #6	$213.71	10.585%	$236.3312	$236.33	$236.35	$236.30
Purchase #7	$139.84	11.158%	$155.4433	$155.44	$155.45	$155.40
7 purchase totals =	$865.84		$956.5820	$956.58	$956.60	$956.50