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	$22.36	10.825%	$24.7805	$24.78	$24.80	$24.80
Purchase #2	$168.55	5.688%	$178.1371	$178.14	$178.15	$178.10
Purchase #3	$131.40	8.717%	$142.8541	$142.85	$142.85	$142.90
Purchase #4	$67.37	6.164%	$71.5227	$71.52	$71.50	$71.50
Purchase #5	$217.44	12.661%	$244.9701	$244.97	$244.95	$245.00
Purchase #6	$237.52	8.871%	$258.5904	$258.59	$258.60	$258.60
Purchase #7	$119.49	7.627%	$128.6035	$128.60	$128.60	$128.60
7 purchase totals =	$964.13		$1,049.4584	$1,049.45	$1,049.45	$1,049.50