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	$46.50	11.844%	$52.0075	$52.01	$52.00	$52.00
Purchase #2	$164.51	6.752%	$175.6177	$175.62	$175.60	$175.60
Purchase #3	$12.31	8.798%	$13.393	$13.39	$13.40	$13.40
Purchase #4	$104.60	4.259%	$109.0549	$109.05	$109.05	$109.10
Purchase #5	$173.81	3.745%	$180.3192	$180.32	$180.30	$180.30
Purchase #6	$233.87	11.637%	$261.0855	$261.09	$261.10	$261.10
Purchase #7	$63.29	11.215%	$70.388	$70.39	$70.40	$70.40
7 purchase totals =	$798.89		$861.8658	$861.87	$861.85	$861.90