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	$144.92	9.636%	$158.8845	$158.88	$158.90	$158.90
Purchase #2	$123.83	5.827%	$131.0456	$131.05	$131.05	$131.00
Purchase #3	$120.84	5.475%	$127.456	$127.46	$127.45	$127.50
Purchase #4	$199.33	5.388%	$210.0699	$210.07	$210.05	$210.10
Purchase #5	$117.28	7.824%	$126.456	$126.46	$126.45	$126.50
Purchase #6	$14.30	7.635%	$15.3918	$15.39	$15.40	$15.40
Purchase #7	$120.45	3.541%	$124.7151	$124.72	$124.70	$124.70
7 purchase totals =	$840.95		$894.0189	$894.03	$894.00	$894.10