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	$41.78	4.195%	$43.5327	$43.53	$43.55	$43.50
Purchase #2	$52.58	13.776%	$59.8234	$59.82	$59.80	$59.80
Purchase #3	$123.59	13.630%	$140.4353	$140.44	$140.45	$140.40
Purchase #4	$137.66	10.442%	$152.0345	$152.03	$152.05	$152.00
Purchase #5	$169.29	13.532%	$192.1983	$192.20	$192.20	$192.20
Purchase #6	$182.31	9.710%	$200.0123	$200.01	$200.00	$200.00
Purchase #7	$87.38	7.137%	$93.6163	$93.62	$93.60	$93.60
7 purchase totals =	$794.59		$881.6528	$881.65	$881.65	$881.50