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	$218.26	3.396%	$225.6721	$225.67	$225.65	$225.70
Purchase #2	$165.60	7.808%	$178.53	$178.53	$178.55	$178.50
Purchase #3	$132.32	8.274%	$143.2682	$143.27	$143.25	$143.30
Purchase #4	$16.58	12.863%	$18.7127	$18.71	$18.70	$18.70
Purchase #5	$111.59	10.630%	$123.452	$123.45	$123.45	$123.50
Purchase #6	$6.66	6.823%	$7.1144	$7.11	$7.10	$7.10
Purchase #7	$74.60	4.399%	$77.8817	$77.88	$77.90	$77.90
7 purchase totals =	$725.61		$774.6311	$774.62	$774.60	$774.70