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	$127.72	10.638%	$141.3069	$141.31	$141.30	$141.30
Purchase #2	$93.31	12.755%	$105.2117	$105.21	$105.20	$105.20
Purchase #3	$33.97	8.675%	$36.9169	$36.92	$36.90	$36.90
Purchase #4	$153.61	11.662%	$171.524	$171.52	$171.50	$171.50
Purchase #5	$81.78	13.250%	$92.6159	$92.62	$92.60	$92.60
Purchase #6	$11.39	10.643%	$12.6022	$12.60	$12.60	$12.60
Purchase #7	$234.72	9.651%	$257.3728	$257.37	$257.35	$257.40
7 purchase totals =	$736.50		$817.5504	$817.55	$817.45	$817.50