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	$164.85	12.510%	$185.4727	$185.47	$185.45	$185.50
Purchase #2	$76.72	7.475%	$82.4548	$82.45	$82.45	$82.50
Purchase #3	$17.27	8.433%	$18.7264	$18.73	$18.75	$18.70
Purchase #4	$158.54	5.557%	$167.3501	$167.35	$167.35	$167.40
Purchase #5	$73.51	4.305%	$76.6746	$76.67	$76.65	$76.70
Purchase #6	$161.77	11.868%	$180.9689	$180.97	$180.95	$181.00
Purchase #7	$58.25	7.493%	$62.6147	$62.61	$62.60	$62.60
7 purchase totals =	$710.91		$774.2622	$774.25	$774.20	$774.40