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	$66.93	9.516%	$73.2991	$73.30	$73.30	$73.30
Purchase #2	$151.76	3.338%	$156.8257	$156.83	$156.85	$156.80
Purchase #3	$205.28	4.686%	$214.8994	$214.90	$214.90	$214.90
Purchase #4	$30.98	12.333%	$34.8008	$34.80	$34.80	$34.80
Purchase #5	$166.76	3.613%	$172.785	$172.79	$172.80	$172.80
Purchase #6	$172.51	7.557%	$185.5466	$185.55	$185.55	$185.50
Purchase #7	$103.83	5.634%	$109.6798	$109.68	$109.70	$109.70
7 purchase totals =	$898.05		$947.8364	$947.85	$947.90	$947.80