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	$108.29	11.832%	$121.1029	$121.10	$121.10	$121.10
Purchase #2	$64.96	4.423%	$67.8332	$67.83	$67.85	$67.80
Purchase #3	$164.85	12.255%	$185.0524	$185.05	$185.05	$185.10
Purchase #4	$158.30	6.277%	$168.2365	$168.24	$168.25	$168.20
Purchase #5	$204.89	13.269%	$232.0769	$232.08	$232.10	$232.10
Purchase #6	$158.84	8.203%	$171.8696	$171.87	$171.85	$171.90
Purchase #7	$117.70	4.872%	$123.4343	$123.43	$123.45	$123.40
7 purchase totals =	$977.83		$1,069.6058	$1,069.60	$1,069.65	$1,069.60