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	$185.61	13.275%	$210.2497	$210.25	$210.25	$210.20
Purchase #2	$105.30	3.765%	$109.2645	$109.26	$109.25	$109.30
Purchase #3	$219.87	5.193%	$231.2878	$231.29	$231.30	$231.30
Purchase #4	$134.83	10.216%	$148.6042	$148.60	$148.60	$148.60
Purchase #5	$228.62	11.286%	$254.4221	$254.42	$254.40	$254.40
Purchase #6	$52.93	12.360%	$59.4721	$59.47	$59.45	$59.50
Purchase #7	$168.54	8.461%	$182.8002	$182.80	$182.80	$182.80
7 purchase totals =	$1,095.70		$1,196.1006	$1,196.09	$1,196.05	$1,196.10