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	$241.65	10.450%	$266.9024	$266.90	$266.90	$266.90
Purchase #2	$43.56	3.368%	$45.0271	$45.03	$45.05	$45.00
Purchase #3	$137.31	13.261%	$155.5187	$155.52	$155.50	$155.50
Purchase #4	$228.68	9.136%	$249.5722	$249.57	$249.55	$249.60
Purchase #5	$73.85	11.816%	$82.5761	$82.58	$82.60	$82.60
Purchase #6	$80.98	4.815%	$84.8792	$84.88	$84.90	$84.90
Purchase #7	$240.90	6.508%	$256.5778	$256.58	$256.60	$256.60
7 purchase totals =	$1,046.93		$1,141.0535	$1,141.06	$1,141.10	$1,141.10