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	$219.45	4.597%	$229.5381	$229.54	$229.55	$229.50
Purchase #2	$200.39	13.214%	$226.8695	$226.87	$226.85	$226.90
Purchase #3	$94.94	10.268%	$104.6884	$104.69	$104.70	$104.70
Purchase #4	$219.42	7.807%	$236.5501	$236.55	$236.55	$236.60
Purchase #5	$53.35	5.692%	$56.3867	$56.39	$56.40	$56.40
Purchase #6	$151.50	12.188%	$169.9648	$169.96	$169.95	$170.00
Purchase #7	$52.71	7.234%	$56.523	$56.52	$56.50	$56.50
7 purchase totals =	$991.76		$1,080.5206	$1,080.52	$1,080.50	$1,080.60