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	$161.49	6.161%	$171.4394	$171.44	$171.45	$171.40
Purchase #2	$210.49	3.402%	$217.6509	$217.65	$217.65	$217.70
Purchase #3	$248.63	13.682%	$282.6476	$282.65	$282.65	$282.60
Purchase #4	$47.92	5.589%	$50.5982	$50.60	$50.60	$50.60
Purchase #5	$36.59	9.645%	$40.1191	$40.12	$40.10	$40.10
Purchase #6	$185.69	10.758%	$205.6665	$205.67	$205.65	$205.70
Purchase #7	$45.52	12.230%	$51.0871	$51.09	$51.10	$51.10
7 purchase totals =	$936.33		$1,019.2088	$1,019.22	$1,019.20	$1,019.20