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	$197.36	12.765%	$222.553	$222.55	$222.55	$222.60
Purchase #2	$191.99	11.768%	$214.5834	$214.58	$214.60	$214.60
Purchase #3	$144.51	8.473%	$156.7543	$156.75	$156.75	$156.80
Purchase #4	$65.32	4.209%	$68.0693	$68.07	$68.05	$68.10
Purchase #5	$43.71	4.153%	$45.5253	$45.53	$45.55	$45.50
Purchase #6	$127.30	3.135%	$131.2909	$131.29	$131.30	$131.30
Purchase #7	$244.46	9.154%	$266.8379	$266.84	$266.85	$266.80
7 purchase totals =	$1,014.65		$1,105.6141	$1,105.61	$1,105.65	$1,105.70