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	$214.65	7.834%	$231.4657	$231.47	$231.45	$231.50
Purchase #2	$166.54	12.577%	$187.4857	$187.49	$187.50	$187.50
Purchase #3	$146.56	10.844%	$162.453	$162.45	$162.45	$162.50
Purchase #4	$69.86	3.232%	$72.1179	$72.12	$72.10	$72.10
Purchase #5	$144.40	5.273%	$152.0142	$152.01	$152.00	$152.00
Purchase #6	$218.62	8.775%	$237.8039	$237.80	$237.80	$237.80
Purchase #7	$46.71	8.149%	$50.5164	$50.52	$50.50	$50.50
7 purchase totals =	$1,007.34		$1,093.8568	$1,093.86	$1,093.80	$1,093.90