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	$82.86	8.157%	$89.6189	$89.62	$89.60	$89.60
Purchase #2	$148.54	7.764%	$160.0726	$160.07	$160.05	$160.10
Purchase #3	$232.63	10.665%	$257.44	$257.44	$257.45	$257.40
Purchase #4	$20.32	7.544%	$21.8529	$21.85	$21.85	$21.90
Purchase #5	$146.93	5.278%	$154.685	$154.69	$154.70	$154.70
Purchase #6	$168.93	11.233%	$187.9059	$187.91	$187.90	$187.90
Purchase #7	$95.83	11.209%	$106.5716	$106.57	$106.55	$106.60
7 purchase totals =	$896.04		$978.1469	$978.15	$978.10	$978.20