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	$123.56	6.756%	$131.9077	$131.91	$131.90	$131.90
Purchase #2	$59.40	5.440%	$62.6314	$62.63	$62.65	$62.60
Purchase #3	$139.90	10.274%	$154.2733	$154.27	$154.25	$154.30
Purchase #4	$91.66	3.208%	$94.6005	$94.60	$94.60	$94.60
Purchase #5	$156.48	12.571%	$176.1511	$176.15	$176.15	$176.20
Purchase #6	$229.25	9.837%	$251.8013	$251.80	$251.80	$251.80
Purchase #7	$146.81	4.712%	$153.7277	$153.73	$153.75	$153.70
7 purchase totals =	$947.06		$1,025.0930	$1,025.09	$1,025.10	$1,025.10