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	$86.69	6.481%	$92.3084	$92.31	$92.30	$92.30
Purchase #2	$239.58	13.328%	$271.5112	$271.51	$271.50	$271.50
Purchase #3	$214.96	3.307%	$222.0687	$222.07	$222.05	$222.10
Purchase #4	$111.67	5.432%	$117.7359	$117.74	$117.75	$117.70
Purchase #5	$103.61	13.183%	$117.2689	$117.27	$117.25	$117.30
Purchase #6	$104.55	11.410%	$116.4792	$116.48	$116.50	$116.50
Purchase #7	$108.87	9.372%	$119.0733	$119.07	$119.05	$119.10
7 purchase totals =	$969.93		$1,056.4456	$1,056.45	$1,056.40	$1,056.50