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	$64.67	9.509%	$70.8195	$70.82	$70.80	$70.80
Purchase #2	$222.52	6.517%	$237.0216	$237.02	$237.00	$237.00
Purchase #3	$125.40	13.692%	$142.5698	$142.57	$142.55	$142.60
Purchase #4	$48.83	9.745%	$53.5885	$53.59	$53.60	$53.60
Purchase #5	$33.48	7.121%	$35.8641	$35.86	$35.85	$35.90
Purchase #6	$42.45	7.812%	$45.7662	$45.77	$45.75	$45.80
Purchase #7	$20.92	3.722%	$21.6986	$21.70	$21.70	$21.70
7 purchase totals =	$558.27		$607.3283	$607.33	$607.25	$607.40