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	$77.82	9.304%	$85.0604	$85.06	$85.05	$85.10
Purchase #2	$91.56	4.162%	$95.3707	$95.37	$95.35	$95.40
Purchase #3	$96.76	4.381%	$100.9991	$101.00	$101.00	$101.00
Purchase #4	$148.64	8.438%	$161.1822	$161.18	$161.20	$161.20
Purchase #5	$179.91	10.598%	$198.9769	$198.98	$199.00	$199.00
Purchase #6	$127.63	13.520%	$144.8856	$144.89	$144.90	$144.90
Purchase #7	$37.45	13.271%	$42.42	$42.42	$42.40	$42.40
7 purchase totals =	$759.77		$828.8949	$828.90	$828.90	$829.00