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	$116.40	11.693%	$130.0107	$130.01	$130.00	$130.00
Purchase #2	$78.45	10.204%	$86.455	$86.46	$86.45	$86.50
Purchase #3	$17.25	7.530%	$18.5489	$18.55	$18.55	$18.50
Purchase #4	$194.52	11.703%	$217.2847	$217.28	$217.30	$217.30
Purchase #5	$100.85	9.462%	$110.3924	$110.39	$110.40	$110.40
Purchase #6	$87.63	12.781%	$98.83	$98.83	$98.85	$98.80
Purchase #7	$18.89	10.628%	$20.8976	$20.90	$20.90	$20.90
7 purchase totals =	$613.99		$682.4193	$682.42	$682.45	$682.40