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	$40.89	13.553%	$46.4318	$46.43	$46.45	$46.40
Purchase #2	$199.29	3.187%	$205.6414	$205.64	$205.65	$205.60
Purchase #3	$103.80	12.367%	$116.6369	$116.64	$116.65	$116.60
Purchase #4	$227.68	7.450%	$244.6422	$244.64	$244.65	$244.60
Purchase #5	$246.38	5.857%	$260.8105	$260.81	$260.80	$260.80
Purchase #6	$99.56	3.601%	$103.1452	$103.15	$103.15	$103.10
Purchase #7	$57.61	8.608%	$62.5691	$62.57	$62.55	$62.60
7 purchase totals =	$975.21		$1,039.8771	$1,039.88	$1,039.90	$1,039.70