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	$98.50	10.211%	$108.5578	$108.56	$108.55	$108.60
Purchase #2	$79.83	8.384%	$86.5229	$86.52	$86.50	$86.50
Purchase #3	$232.34	10.416%	$256.5405	$256.54	$256.55	$256.50
Purchase #4	$144.67	6.775%	$154.4714	$154.47	$154.45	$154.50
Purchase #5	$204.93	12.836%	$231.2348	$231.23	$231.25	$231.20
Purchase #6	$168.39	12.785%	$189.9187	$189.92	$189.90	$189.90
Purchase #7	$101.42	13.166%	$114.773	$114.77	$114.75	$114.80
7 purchase totals =	$1,030.08		$1,142.0191	$1,142.01	$1,141.95	$1,142.00