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	$111.64	4.164%	$116.2887	$116.29	$116.30	$116.30
Purchase #2	$218.85	5.311%	$230.4731	$230.47	$230.45	$230.50
Purchase #3	$30.27	3.385%	$31.2946	$31.29	$31.30	$31.30
Purchase #4	$84.42	11.408%	$94.0506	$94.05	$94.05	$94.10
Purchase #5	$170.90	13.568%	$194.0877	$194.09	$194.10	$194.10
Purchase #6	$248.62	3.392%	$257.0532	$257.05	$257.05	$257.10
Purchase #7	$78.97	13.307%	$89.4785	$89.48	$89.50	$89.50
7 purchase totals =	$943.67		$1,012.7264	$1,012.72	$1,012.75	$1,012.90