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	$116.67	12.188%	$130.8897	$130.89	$130.90	$130.90
Purchase #2	$194.39	7.599%	$209.1617	$209.16	$209.15	$209.20
Purchase #3	$100.59	3.189%	$103.7978	$103.80	$103.80	$103.80
Purchase #4	$122.97	6.564%	$131.0418	$131.04	$131.05	$131.00
Purchase #5	$236.33	9.717%	$259.2942	$259.29	$259.30	$259.30
Purchase #6	$123.35	5.189%	$129.7506	$129.75	$129.75	$129.80
Purchase #7	$172.79	4.709%	$180.9267	$180.93	$180.95	$180.90
7 purchase totals =	$1,067.09		$1,144.8625	$1,144.86	$1,144.90	$1,144.90