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	$184.29	13.396%	$208.9775	$208.98	$209.00	$209.00
Purchase #2	$128.75	12.373%	$144.6802	$144.68	$144.70	$144.70
Purchase #3	$135.85	7.638%	$146.2262	$146.23	$146.25	$146.20
Purchase #4	$44.81	4.508%	$46.83	$46.83	$46.85	$46.80
Purchase #5	$240.54	4.208%	$250.6619	$250.66	$250.65	$250.70
Purchase #6	$159.95	5.577%	$168.8704	$168.87	$168.85	$168.90
Purchase #7	$163.74	9.490%	$179.2789	$179.28	$179.30	$179.30
7 purchase totals =	$1,057.93		$1,145.5251	$1,145.53	$1,145.60	$1,145.60