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	$132.97	3.447%	$137.5535	$137.55	$137.55	$137.60
Purchase #2	$192.80	6.464%	$205.2626	$205.26	$205.25	$205.30
Purchase #3	$42.30	4.325%	$44.1295	$44.13	$44.15	$44.10
Purchase #4	$20.83	4.540%	$21.7757	$21.78	$21.80	$21.80
Purchase #5	$176.72	7.780%	$190.4688	$190.47	$190.45	$190.50
Purchase #6	$224.71	13.295%	$254.5852	$254.59	$254.60	$254.60
Purchase #7	$136.83	13.799%	$155.7112	$155.71	$155.70	$155.70
7 purchase totals =	$927.16		$1,009.4865	$1,009.49	$1,009.50	$1,009.60