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	$157.66	9.659%	$172.8884	$172.89	$172.90	$172.90
Purchase #2	$183.59	5.694%	$194.0436	$194.04	$194.05	$194.00
Purchase #3	$15.81	11.147%	$17.5723	$17.57	$17.55	$17.60
Purchase #4	$162.93	13.301%	$184.6013	$184.60	$184.60	$184.60
Purchase #5	$98.69	9.425%	$107.9915	$107.99	$108.00	$108.00
Purchase #6	$49.61	9.490%	$54.318	$54.32	$54.30	$54.30
Purchase #7	$196.39	13.815%	$223.5213	$223.52	$223.50	$223.50
7 purchase totals =	$864.68		$954.9364	$954.93	$954.90	$954.90