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	$229.85	12.587%	$258.7812	$258.78	$258.80	$258.80
Purchase #2	$233.95	9.193%	$255.457	$255.46	$255.45	$255.50
Purchase #3	$38.25	6.349%	$40.6785	$40.68	$40.70	$40.70
Purchase #4	$145.42	5.790%	$153.8398	$153.84	$153.85	$153.80
Purchase #5	$90.97	7.186%	$97.5071	$97.51	$97.50	$97.50
Purchase #6	$193.47	6.253%	$205.5677	$205.57	$205.55	$205.60
Purchase #7	$71.53	4.123%	$74.4792	$74.48	$74.50	$74.50
7 purchase totals =	$1,003.44		$1,086.3105	$1,086.32	$1,086.35	$1,086.40