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	$210.26	11.126%	$233.6535	$233.65	$233.65	$233.70
Purchase #2	$94.75	3.871%	$98.4178	$98.42	$98.40	$98.40
Purchase #3	$108.59	8.577%	$117.9038	$117.90	$117.90	$117.90
Purchase #4	$228.42	12.135%	$256.1388	$256.14	$256.15	$256.10
Purchase #5	$241.52	9.727%	$265.0127	$265.01	$265.00	$265.00
Purchase #6	$215.55	10.653%	$238.5125	$238.51	$238.50	$238.50
Purchase #7	$105.87	5.661%	$111.8633	$111.86	$111.85	$111.90
7 purchase totals =	$1,204.96		$1,321.5024	$1,321.49	$1,321.45	$1,321.50