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	$191.72	3.808%	$199.0207	$199.02	$199.00	$199.00
Purchase #2	$61.32	7.675%	$66.0263	$66.03	$66.05	$66.00
Purchase #3	$48.31	6.163%	$51.2873	$51.29	$51.30	$51.30
Purchase #4	$49.49	9.136%	$54.0114	$54.01	$54.00	$54.00
Purchase #5	$143.68	8.765%	$156.2736	$156.27	$156.25	$156.30
Purchase #6	$127.54	13.235%	$144.4199	$144.42	$144.40	$144.40
Purchase #7	$227.39	4.438%	$237.4816	$237.48	$237.50	$237.50
7 purchase totals =	$849.45		$908.5208	$908.52	$908.50	$908.50