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	$164.88	8.738%	$179.2872	$179.29	$179.30	$179.30
Purchase #2	$54.54	7.171%	$58.4511	$58.45	$58.45	$58.50
Purchase #3	$92.39	13.139%	$104.5291	$104.53	$104.55	$104.50
Purchase #4	$91.46	5.704%	$96.6769	$96.68	$96.70	$96.70
Purchase #5	$112.50	3.252%	$116.1585	$116.16	$116.15	$116.20
Purchase #6	$100.99	11.267%	$112.3685	$112.37	$112.35	$112.40
Purchase #7	$51.38	4.335%	$53.6073	$53.61	$53.60	$53.60
7 purchase totals =	$668.14		$721.0786	$721.09	$721.10	$721.20