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	$13.78	7.525%	$14.8169	$14.82	$14.80	$14.80
Purchase #2	$174.95	4.559%	$182.926	$182.93	$182.95	$182.90
Purchase #3	$100.85	11.670%	$112.6192	$112.62	$112.60	$112.60
Purchase #4	$87.54	4.334%	$91.334	$91.33	$91.35	$91.30
Purchase #5	$128.79	6.864%	$137.6301	$137.63	$137.65	$137.60
Purchase #6	$245.90	12.337%	$276.2367	$276.24	$276.25	$276.20
Purchase #7	$223.54	11.828%	$249.9803	$249.98	$250.00	$250.00
7 purchase totals =	$975.35		$1,065.5432	$1,065.55	$1,065.60	$1,065.40