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	$81.25	5.401%	$85.6383	$85.64	$85.65	$85.60
Purchase #2	$148.79	3.829%	$154.4872	$154.49	$154.50	$154.50
Purchase #3	$62.54	11.149%	$69.5126	$69.51	$69.50	$69.50
Purchase #4	$117.92	13.843%	$134.2437	$134.24	$134.25	$134.20
Purchase #5	$39.59	6.819%	$42.2896	$42.29	$42.30	$42.30
Purchase #6	$236.53	10.194%	$260.6419	$260.64	$260.65	$260.60
Purchase #7	$41.28	13.330%	$46.7826	$46.78	$46.80	$46.80
7 purchase totals =	$727.90		$793.5959	$793.59	$793.65	$793.50