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	$120.76	9.714%	$132.4906	$132.49	$132.50	$132.50
Purchase #2	$245.42	8.198%	$265.5395	$265.54	$265.55	$265.50
Purchase #3	$143.65	4.349%	$149.8973	$149.90	$149.90	$149.90
Purchase #4	$122.78	3.589%	$127.1866	$127.19	$127.20	$127.20
Purchase #5	$127.71	13.421%	$144.85	$144.85	$144.85	$144.90
Purchase #6	$20.82	12.335%	$23.3881	$23.39	$23.40	$23.40
Purchase #7	$217.85	11.593%	$243.1054	$243.11	$243.10	$243.10
7 purchase totals =	$998.99		$1,086.4575	$1,086.47	$1,086.50	$1,086.50