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	$112.74	5.399%	$118.8268	$118.83	$118.85	$118.80
Purchase #2	$105.46	7.284%	$113.1417	$113.14	$113.15	$113.10
Purchase #3	$112.89	9.798%	$123.951	$123.95	$123.95	$124.00
Purchase #4	$59.42	5.766%	$62.8462	$62.85	$62.85	$62.80
Purchase #5	$224.46	3.135%	$231.4968	$231.50	$231.50	$231.50
Purchase #6	$136.53	3.471%	$141.269	$141.27	$141.25	$141.30
Purchase #7	$87.52	9.194%	$95.5666	$95.57	$95.55	$95.60
7 purchase totals =	$839.02		$887.0981	$887.11	$887.10	$887.10