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	$98.53	13.323%	$111.6572	$111.66	$111.65	$111.70
Purchase #2	$130.63	5.607%	$137.9544	$137.95	$137.95	$138.00
Purchase #3	$209.30	12.676%	$235.8309	$235.83	$235.85	$235.80
Purchase #4	$228.39	10.203%	$251.6926	$251.69	$251.70	$251.70
Purchase #5	$78.73	11.567%	$87.8367	$87.84	$87.85	$87.80
Purchase #6	$167.43	9.559%	$183.4346	$183.43	$183.45	$183.40
Purchase #7	$55.81	5.824%	$59.0604	$59.06	$59.05	$59.10
7 purchase totals =	$968.82		$1,067.4668	$1,067.46	$1,067.50	$1,067.50