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	$78.99	10.703%	$87.4443	$87.44	$87.45	$87.40
Purchase #2	$78.32	5.555%	$82.6707	$82.67	$82.65	$82.70
Purchase #3	$87.77	3.413%	$90.7656	$90.77	$90.75	$90.80
Purchase #4	$118.85	8.152%	$128.5387	$128.54	$128.55	$128.50
Purchase #5	$250.79	5.820%	$265.386	$265.39	$265.40	$265.40
Purchase #6	$41.53	6.871%	$44.3835	$44.38	$44.40	$44.40
Purchase #7	$240.76	4.803%	$252.3237	$252.32	$252.30	$252.30
7 purchase totals =	$897.01		$951.5125	$951.51	$951.50	$951.50