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	$207.60	8.151%	$224.5215	$224.52	$224.50	$224.50
Purchase #2	$213.94	11.510%	$238.5645	$238.56	$238.55	$238.60
Purchase #3	$51.58	6.553%	$54.96	$54.96	$54.95	$55.00
Purchase #4	$152.53	3.261%	$157.504	$157.50	$157.50	$157.50
Purchase #5	$64.67	11.585%	$72.162	$72.16	$72.15	$72.20
Purchase #6	$124.50	12.546%	$140.1198	$140.12	$140.10	$140.10
Purchase #7	$240.25	4.849%	$251.8997	$251.90	$251.90	$251.90
7 purchase totals =	$1,055.07		$1,139.7315	$1,139.72	$1,139.65	$1,139.80