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	$187.89	6.712%	$200.5012	$200.50	$200.50	$200.50
Purchase #2	$48.72	7.529%	$52.3881	$52.39	$52.40	$52.40
Purchase #3	$114.81	7.386%	$123.2899	$123.29	$123.30	$123.30
Purchase #4	$238.70	13.264%	$270.3612	$270.36	$270.35	$270.40
Purchase #5	$217.56	11.142%	$241.8005	$241.80	$241.80	$241.80
Purchase #6	$95.49	9.193%	$104.2684	$104.27	$104.25	$104.30
Purchase #7	$102.96	8.398%	$111.6066	$111.61	$111.60	$111.60
7 purchase totals =	$1,006.13		$1,104.2159	$1,104.22	$1,104.20	$1,104.30