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	$160.95	3.698%	$166.9019	$166.90	$166.90	$166.90
Purchase #2	$198.78	3.555%	$205.8466	$205.85	$205.85	$205.80
Purchase #3	$18.32	4.299%	$19.1076	$19.11	$19.10	$19.10
Purchase #4	$41.57	5.123%	$43.6996	$43.70	$43.70	$43.70
Purchase #5	$69.90	5.144%	$73.4957	$73.50	$73.50	$73.50
Purchase #6	$12.33	13.814%	$14.0333	$14.03	$14.05	$14.00
Purchase #7	$52.90	4.831%	$55.4556	$55.46	$55.45	$55.50
7 purchase totals =	$554.75		$578.5403	$578.55	$578.55	$578.50