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	$177.45	13.237%	$200.9391	$200.94	$200.95	$200.90
Purchase #2	$240.75	10.138%	$265.1572	$265.16	$265.15	$265.20
Purchase #3	$166.74	9.636%	$182.8071	$182.81	$182.80	$182.80
Purchase #4	$168.40	8.627%	$182.9279	$182.93	$182.95	$182.90
Purchase #5	$99.35	8.552%	$107.8464	$107.85	$107.85	$107.80
Purchase #6	$6.83	6.598%	$7.2806	$7.28	$7.30	$7.30
Purchase #7	$118.85	10.686%	$131.5503	$131.55	$131.55	$131.60
7 purchase totals =	$978.37		$1,078.5086	$1,078.52	$1,078.55	$1,078.50