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	$177.61	12.237%	$199.3441	$199.34	$199.35	$199.30
Purchase #2	$123.89	8.747%	$134.7267	$134.73	$134.75	$134.70
Purchase #3	$224.94	7.175%	$241.0794	$241.08	$241.10	$241.10
Purchase #4	$161.56	12.846%	$182.314	$182.31	$182.30	$182.30
Purchase #5	$115.78	9.599%	$126.8937	$126.89	$126.90	$126.90
Purchase #6	$60.28	11.798%	$67.3918	$67.39	$67.40	$67.40
Purchase #7	$42.33	10.517%	$46.7818	$46.78	$46.80	$46.80
7 purchase totals =	$906.39		$998.5315	$998.52	$998.60	$998.50