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	$45.89	4.432%	$47.9238	$47.92	$47.90	$47.90
Purchase #2	$166.60	5.324%	$175.4698	$175.47	$175.45	$175.50
Purchase #3	$15.68	13.826%	$17.8479	$17.85	$17.85	$17.80
Purchase #4	$217.39	7.418%	$233.516	$233.52	$233.50	$233.50
Purchase #5	$88.50	6.590%	$94.3322	$94.33	$94.35	$94.30
Purchase #6	$12.64	10.162%	$13.9245	$13.92	$13.90	$13.90
Purchase #7	$145.27	13.309%	$164.604	$164.60	$164.60	$164.60
7 purchase totals =	$691.97		$747.6182	$747.61	$747.55	$747.50