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	$166.29	5.467%	$175.3811	$175.38	$175.40	$175.40
Purchase #2	$187.60	4.817%	$196.6367	$196.64	$196.65	$196.60
Purchase #3	$96.83	7.825%	$104.4069	$104.41	$104.40	$104.40
Purchase #4	$60.84	8.538%	$66.0345	$66.03	$66.05	$66.00
Purchase #5	$114.82	4.709%	$120.2269	$120.23	$120.25	$120.20
Purchase #6	$76.70	9.256%	$83.7994	$83.80	$83.80	$83.80
Purchase #7	$127.71	12.601%	$143.8027	$143.80	$143.80	$143.80
7 purchase totals =	$830.79		$890.2882	$890.29	$890.35	$890.20