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	$144.34	11.212%	$160.5234	$160.52	$160.50	$160.50
Purchase #2	$37.96	10.656%	$42.005	$42.01	$42.00	$42.00
Purchase #3	$100.31	11.372%	$111.7173	$111.72	$111.70	$111.70
Purchase #4	$69.93	9.868%	$76.8307	$76.83	$76.85	$76.80
Purchase #5	$40.63	9.463%	$44.4748	$44.47	$44.45	$44.50
Purchase #6	$233.94	7.330%	$251.0878	$251.09	$251.10	$251.10
Purchase #7	$63.37	5.568%	$66.8984	$66.90	$66.90	$66.90
7 purchase totals =	$690.48		$753.5374	$753.54	$753.50	$753.50