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	$156.93	6.336%	$166.8731	$166.87	$166.85	$166.90
Purchase #2	$152.70	6.473%	$162.5843	$162.58	$162.60	$162.60
Purchase #3	$117.64	5.121%	$123.6643	$123.66	$123.65	$123.70
Purchase #4	$101.85	12.713%	$114.7982	$114.80	$114.80	$114.80
Purchase #5	$15.60	12.240%	$17.5094	$17.51	$17.50	$17.50
Purchase #6	$249.65	12.420%	$280.6565	$280.66	$280.65	$280.70
Purchase #7	$166.95	10.103%	$183.817	$183.82	$183.80	$183.80
7 purchase totals =	$961.32		$1,049.9028	$1,049.90	$1,049.85	$1,050.00