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	$219.79	5.417%	$231.696	$231.70	$231.70	$231.70
Purchase #2	$51.46	11.857%	$57.5616	$57.56	$57.55	$57.60
Purchase #3	$29.26	7.311%	$31.3992	$31.40	$31.40	$31.40
Purchase #4	$38.49	11.534%	$42.9294	$42.93	$42.95	$42.90
Purchase #5	$241.52	5.772%	$255.4605	$255.46	$255.45	$255.50
Purchase #6	$208.31	4.230%	$217.1215	$217.12	$217.10	$217.10
Purchase #7	$111.55	3.401%	$115.3438	$115.34	$115.35	$115.30
7 purchase totals =	$900.38		$951.5120	$951.51	$951.50	$951.50