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	$157.78	13.738%	$179.4558	$179.46	$179.45	$179.50
Purchase #2	$191.84	6.867%	$205.0137	$205.01	$205.00	$205.00
Purchase #3	$137.92	10.554%	$152.4761	$152.48	$152.50	$152.50
Purchase #4	$80.80	8.125%	$87.365	$87.37	$87.35	$87.40
Purchase #5	$72.43	6.451%	$77.1025	$77.10	$77.10	$77.10
Purchase #6	$147.85	11.164%	$164.356	$164.36	$164.35	$164.40
Purchase #7	$140.41	9.383%	$153.5847	$153.58	$153.60	$153.60
7 purchase totals =	$929.03		$1,019.3538	$1,019.36	$1,019.35	$1,019.50