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	$47.98	9.196%	$52.3922	$52.39	$52.40	$52.40
Purchase #2	$118.44	4.236%	$123.4571	$123.46	$123.45	$123.50
Purchase #3	$132.47	12.427%	$148.932	$148.93	$148.95	$148.90
Purchase #4	$65.77	12.291%	$73.8538	$73.85	$73.85	$73.90
Purchase #5	$242.27	10.794%	$268.4206	$268.42	$268.40	$268.40
Purchase #6	$194.36	5.160%	$204.389	$204.39	$204.40	$204.40
Purchase #7	$107.98	3.672%	$111.945	$111.95	$111.95	$111.90
7 purchase totals =	$909.27		$983.3897	$983.39	$983.40	$983.40