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	$123.92	5.714%	$131.0008	$131.00	$131.00	$131.00
Purchase #2	$19.38	13.319%	$21.9612	$21.96	$21.95	$22.00
Purchase #3	$187.26	11.420%	$208.6451	$208.65	$208.65	$208.60
Purchase #4	$117.77	5.160%	$123.8469	$123.85	$123.85	$123.80
Purchase #5	$162.84	6.312%	$173.1185	$173.12	$173.10	$173.10
Purchase #6	$133.46	11.587%	$148.924	$148.92	$148.90	$148.90
Purchase #7	$154.87	9.314%	$169.2946	$169.29	$169.30	$169.30
7 purchase totals =	$899.50		$976.7911	$976.79	$976.75	$976.70