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	$38.98	5.534%	$41.1372	$41.14	$41.15	$41.10
Purchase #2	$190.32	13.228%	$215.4955	$215.50	$215.50	$215.50
Purchase #3	$32.70	4.721%	$34.2438	$34.24	$34.25	$34.20
Purchase #4	$65.71	10.826%	$72.8238	$72.82	$72.80	$72.80
Purchase #5	$217.75	12.530%	$245.0341	$245.03	$245.05	$245.00
Purchase #6	$224.69	6.241%	$238.7129	$238.71	$238.70	$238.70
Purchase #7	$135.35	9.457%	$148.15	$148.15	$148.15	$148.20
7 purchase totals =	$905.50		$995.5973	$995.59	$995.60	$995.50