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	$28.69	4.348%	$29.9374	$29.94	$29.95	$29.90
Purchase #2	$172.53	13.339%	$195.5438	$195.54	$195.55	$195.50
Purchase #3	$144.51	10.498%	$159.6807	$159.68	$159.70	$159.70
Purchase #4	$235.66	11.296%	$262.2802	$262.28	$262.30	$262.30
Purchase #5	$200.98	10.491%	$222.0648	$222.06	$222.05	$222.10
Purchase #6	$38.95	3.632%	$40.3647	$40.36	$40.35	$40.40
Purchase #7	$81.25	12.870%	$91.7069	$91.71	$91.70	$91.70
7 purchase totals =	$902.57		$1,001.5785	$1,001.57	$1,001.60	$1,001.60