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	11.106%	$206.2238	$206.22	$206.20	$206.20
Purchase #2	$43.92	10.170%	$48.3867	$48.39	$48.40	$48.40
Purchase #3	$45.89	13.106%	$51.9043	$51.90	$51.90	$51.90
Purchase #4	$238.36	8.492%	$258.6015	$258.60	$258.60	$258.60
Purchase #5	$97.56	6.204%	$103.6126	$103.61	$103.60	$103.60
Purchase #6	$173.72	7.859%	$187.3727	$187.37	$187.35	$187.40
Purchase #7	$7.96	6.514%	$8.4785	$8.48	$8.50	$8.50
7 purchase totals =	$793.02		$864.5801	$864.57	$864.55	$864.60