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	$167.69	13.701%	$190.6652	$190.67	$190.65	$190.70
Purchase #2	$177.83	12.710%	$200.4322	$200.43	$200.45	$200.40
Purchase #3	$138.80	8.618%	$150.7618	$150.76	$150.75	$150.80
Purchase #4	$184.57	11.235%	$205.3064	$205.31	$205.30	$205.30
Purchase #5	$151.95	9.346%	$166.1512	$166.15	$166.15	$166.20
Purchase #6	$235.40	10.107%	$259.1919	$259.19	$259.20	$259.20
Purchase #7	$85.53	4.630%	$89.49	$89.49	$89.50	$89.50
7 purchase totals =	$1,141.77		$1,261.9987	$1,262.00	$1,262.00	$1,262.10