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	$164.50	12.261%	$184.6693	$184.67	$184.65	$184.70
Purchase #2	$168.41	13.367%	$190.9214	$190.92	$190.90	$190.90
Purchase #3	$204.82	11.259%	$227.8807	$227.88	$227.90	$227.90
Purchase #4	$151.81	11.629%	$169.464	$169.46	$169.45	$169.50
Purchase #5	$64.60	13.458%	$73.2939	$73.29	$73.30	$73.30
Purchase #6	$139.93	12.462%	$157.3681	$157.37	$157.35	$157.40
Purchase #7	$11.69	6.138%	$12.4075	$12.41	$12.40	$12.40
7 purchase totals =	$905.76		$1,016.0049	$1,016.00	$1,015.95	$1,016.10