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	$46.67	10.398%	$51.5227	$51.52	$51.50	$51.50
Purchase #2	$144.59	7.660%	$155.6656	$155.67	$155.65	$155.70
Purchase #3	$150.47	10.508%	$166.2814	$166.28	$166.30	$166.30
Purchase #4	$208.55	6.378%	$221.8513	$221.85	$221.85	$221.90
Purchase #5	$180.33	13.687%	$205.0118	$205.01	$205.00	$205.00
Purchase #6	$221.33	10.455%	$244.4701	$244.47	$244.45	$244.50
Purchase #7	$123.54	5.416%	$130.2309	$130.23	$130.25	$130.20
7 purchase totals =	$1,075.48		$1,175.0338	$1,175.03	$1,175.00	$1,175.10