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	$83.83	4.354%	$87.48	$87.48	$87.50	$87.50
Purchase #2	$181.56	9.237%	$198.3307	$198.33	$198.35	$198.30
Purchase #3	$80.68	12.428%	$90.7069	$90.71	$90.70	$90.70
Purchase #4	$194.55	9.715%	$213.4505	$213.45	$213.45	$213.50
Purchase #5	$206.27	6.446%	$219.5662	$219.57	$219.55	$219.60
Purchase #6	$21.60	12.148%	$24.224	$24.22	$24.20	$24.20
Purchase #7	$210.94	10.852%	$233.8312	$233.83	$233.85	$233.80
7 purchase totals =	$979.43		$1,067.5895	$1,067.59	$1,067.60	$1,067.60