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	$180.26	6.738%	$192.4059	$192.41	$192.40	$192.40
Purchase #2	$115.60	7.215%	$123.9405	$123.94	$123.95	$123.90
Purchase #3	$244.59	11.392%	$272.4537	$272.45	$272.45	$272.50
Purchase #4	$151.57	13.808%	$172.4988	$172.50	$172.50	$172.50
Purchase #5	$198.72	6.168%	$210.977	$210.98	$211.00	$211.00
Purchase #6	$20.95	11.627%	$23.3859	$23.39	$23.40	$23.40
Purchase #7	$110.99	10.849%	$123.0313	$123.03	$123.05	$123.00
7 purchase totals =	$1,022.68		$1,118.6931	$1,118.70	$1,118.75	$1,118.70