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	$44.30	5.127%	$46.5713	$46.57	$46.55	$46.60
Purchase #2	$232.49	3.631%	$240.9317	$240.93	$240.95	$240.90
Purchase #3	$27.90	12.646%	$31.4282	$31.43	$31.45	$31.40
Purchase #4	$55.98	11.696%	$62.5274	$62.53	$62.55	$62.50
Purchase #5	$211.50	4.429%	$220.8673	$220.87	$220.85	$220.90
Purchase #6	$166.33	9.124%	$181.5059	$181.51	$181.50	$181.50
Purchase #7	$82.87	3.453%	$85.7315	$85.73	$85.75	$85.70
7 purchase totals =	$821.37		$869.5633	$869.57	$869.60	$869.50