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	$46.97	13.667%	$53.3894	$53.39	$53.40	$53.40
Purchase #2	$104.87	4.561%	$109.6531	$109.65	$109.65	$109.70
Purchase #3	$47.25	9.212%	$51.6027	$51.60	$51.60	$51.60
Purchase #4	$202.40	10.313%	$223.2735	$223.27	$223.25	$223.30
Purchase #5	$208.79	4.141%	$217.436	$217.44	$217.45	$217.40
Purchase #6	$226.32	8.484%	$245.521	$245.52	$245.50	$245.50
Purchase #7	$29.50	7.671%	$31.7629	$31.76	$31.75	$31.80
7 purchase totals =	$866.10		$932.6386	$932.63	$932.60	$932.70