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	$96.57	13.295%	$109.409	$109.41	$109.40	$109.40
Purchase #2	$13.76	12.564%	$15.4888	$15.49	$15.50	$15.50
Purchase #3	$146.62	6.690%	$156.4289	$156.43	$156.45	$156.40
Purchase #4	$244.29	6.429%	$259.9954	$260.00	$260.00	$260.00
Purchase #5	$244.68	13.853%	$278.5755	$278.58	$278.60	$278.60
Purchase #6	$19.66	11.394%	$21.9001	$21.90	$21.90	$21.90
Purchase #7	$43.92	4.386%	$45.8463	$45.85	$45.85	$45.80
7 purchase totals =	$809.50		$887.6440	$887.66	$887.70	$887.60