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	$217.39	3.337%	$224.6443	$224.64	$224.65	$224.60
Purchase #2	$51.77	11.105%	$57.5191	$57.52	$57.50	$57.50
Purchase #3	$175.36	4.378%	$183.0373	$183.04	$183.05	$183.00
Purchase #4	$233.71	10.134%	$257.3942	$257.39	$257.40	$257.40
Purchase #5	$38.94	7.620%	$41.9072	$41.91	$41.90	$41.90
Purchase #6	$219.90	6.573%	$234.354	$234.35	$234.35	$234.40
Purchase #7	$57.36	3.655%	$59.4565	$59.46	$59.45	$59.50
7 purchase totals =	$994.43		$1,058.3126	$1,058.31	$1,058.30	$1,058.30