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	$43.48	8.271%	$47.0762	$47.08	$47.10	$47.10
Purchase #2	$52.98	3.499%	$54.8338	$54.83	$54.85	$54.80
Purchase #3	$166.82	10.216%	$183.8623	$183.86	$183.85	$183.90
Purchase #4	$53.60	4.813%	$56.1798	$56.18	$56.20	$56.20
Purchase #5	$58.77	8.207%	$63.5933	$63.59	$63.60	$63.60
Purchase #6	$159.59	5.470%	$168.3196	$168.32	$168.30	$168.30
Purchase #7	$46.66	12.726%	$52.598	$52.60	$52.60	$52.60
7 purchase totals =	$581.90		$626.4630	$626.46	$626.50	$626.50