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	$98.34	11.326%	$109.478	$109.48	$109.50	$109.50
Purchase #2	$139.95	9.343%	$153.0255	$153.03	$153.05	$153.00
Purchase #3	$205.35	5.436%	$216.5128	$216.51	$216.50	$216.50
Purchase #4	$57.65	12.161%	$64.6608	$64.66	$64.65	$64.70
Purchase #5	$143.48	5.840%	$151.8592	$151.86	$151.85	$151.90
Purchase #6	$120.72	11.105%	$134.126	$134.13	$134.15	$134.10
Purchase #7	$101.40	7.331%	$108.8336	$108.83	$108.85	$108.80
7 purchase totals =	$866.89		$938.4959	$938.50	$938.55	$938.50