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	$237.84	7.825%	$256.451	$256.45	$256.45	$256.50
Purchase #2	$139.65	3.750%	$144.8869	$144.89	$144.90	$144.90
Purchase #3	$39.56	12.283%	$44.4192	$44.42	$44.40	$44.40
Purchase #4	$233.28	8.821%	$253.8576	$253.86	$253.85	$253.90
Purchase #5	$122.79	13.714%	$139.6294	$139.63	$139.65	$139.60
Purchase #6	$139.65	13.271%	$158.183	$158.18	$158.20	$158.20
Purchase #7	$24.54	13.256%	$27.793	$27.79	$27.80	$27.80
7 purchase totals =	$937.31		$1,025.2201	$1,025.22	$1,025.25	$1,025.30