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	$247.36	3.373%	$255.7035	$255.70	$255.70	$255.70
Purchase #2	$22.53	13.504%	$25.5725	$25.57	$25.55	$25.60
Purchase #3	$52.45	13.523%	$59.5428	$59.54	$59.55	$59.50
Purchase #4	$199.95	13.265%	$226.4734	$226.47	$226.45	$226.50
Purchase #5	$90.75	9.373%	$99.256	$99.26	$99.25	$99.30
Purchase #6	$43.77	13.370%	$49.622	$49.62	$49.60	$49.60
Purchase #7	$100.41	3.103%	$103.5257	$103.53	$103.55	$103.50
7 purchase totals =	$757.22		$819.6959	$819.69	$819.65	$819.70