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	$164.73	8.348%	$178.4817	$178.48	$178.50	$178.50
Purchase #2	$53.43	6.475%	$56.8896	$56.89	$56.90	$56.90
Purchase #3	$137.90	5.347%	$145.2735	$145.27	$145.25	$145.30
Purchase #4	$157.60	9.239%	$172.1607	$172.16	$172.15	$172.20
Purchase #5	$224.61	13.745%	$255.4826	$255.48	$255.50	$255.50
Purchase #6	$178.60	4.691%	$186.9781	$186.98	$187.00	$187.00
Purchase #7	$57.89	11.669%	$64.6452	$64.65	$64.65	$64.60
7 purchase totals =	$974.76		$1,059.9114	$1,059.91	$1,059.95	$1,060.00