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	$127.99	4.309%	$133.5051	$133.51	$133.50	$133.50
Purchase #2	$133.82	7.201%	$143.4564	$143.46	$143.45	$143.50
Purchase #3	$133.30	13.557%	$151.3715	$151.37	$151.35	$151.40
Purchase #4	$188.42	3.289%	$194.6171	$194.62	$194.60	$194.60
Purchase #5	$150.37	5.301%	$158.3411	$158.34	$158.35	$158.30
Purchase #6	$144.71	11.661%	$161.5846	$161.58	$161.60	$161.60
Purchase #7	$208.96	3.177%	$215.5987	$215.60	$215.60	$215.60
7 purchase totals =	$1,087.57		$1,158.4745	$1,158.48	$1,158.45	$1,158.50