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	$10.50	10.146%	$11.5653	$11.57	$11.55	$11.60
Purchase #2	$186.89	13.140%	$211.4473	$211.45	$211.45	$211.40
Purchase #3	$84.29	6.808%	$90.0285	$90.03	$90.05	$90.00
Purchase #4	$151.40	13.198%	$171.3818	$171.38	$171.40	$171.40
Purchase #5	$55.88	3.143%	$57.6363	$57.64	$57.65	$57.60
Purchase #6	$211.68	4.213%	$220.5981	$220.60	$220.60	$220.60
Purchase #7	$22.63	3.446%	$23.4098	$23.41	$23.40	$23.40
7 purchase totals =	$723.27		$786.0671	$786.08	$786.10	$786.00