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	$113.95	11.501%	$127.0554	$127.06	$127.05	$127.10
Purchase #2	$107.55	11.804%	$120.2452	$120.25	$120.25	$120.20
Purchase #3	$30.48	3.632%	$31.587	$31.59	$31.60	$31.60
Purchase #4	$102.52	8.572%	$111.308	$111.31	$111.30	$111.30
Purchase #5	$156.44	9.455%	$171.2314	$171.23	$171.25	$171.20
Purchase #6	$34.72	4.605%	$36.3189	$36.32	$36.30	$36.30
Purchase #7	$151.97	12.513%	$170.986	$170.99	$171.00	$171.00
7 purchase totals =	$697.63		$768.7319	$768.75	$768.75	$768.70