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	$165.55	4.385%	$172.8094	$172.81	$172.80	$172.80
Purchase #2	$100.93	11.587%	$112.6248	$112.62	$112.60	$112.60
Purchase #3	$85.90	11.125%	$95.4564	$95.46	$95.45	$95.50
Purchase #4	$5.79	3.809%	$6.0105	$6.01	$6.00	$6.00
Purchase #5	$237.75	7.577%	$255.7643	$255.76	$255.75	$255.80
Purchase #6	$45.67	10.393%	$50.4165	$50.42	$50.40	$50.40
Purchase #7	$104.83	10.151%	$115.4713	$115.47	$115.45	$115.50
7 purchase totals =	$746.42		$808.5532	$808.55	$808.45	$808.60