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	$233.64	6.303%	$248.3663	$248.37	$248.35	$248.40
Purchase #2	$203.76	6.683%	$217.3773	$217.38	$217.40	$217.40
Purchase #3	$180.89	8.505%	$196.2747	$196.27	$196.25	$196.30
Purchase #4	$181.70	10.328%	$200.466	$200.47	$200.45	$200.50
Purchase #5	$13.94	3.650%	$14.4488	$14.45	$14.45	$14.40
Purchase #6	$80.70	3.562%	$83.5745	$83.57	$83.55	$83.60
Purchase #7	$109.35	10.274%	$120.5846	$120.58	$120.60	$120.60
7 purchase totals =	$1,003.98		$1,081.0922	$1,081.09	$1,081.05	$1,081.20