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	$182.84	8.532%	$198.4399	$198.44	$198.45	$198.40
Purchase #2	$49.75	3.243%	$51.3634	$51.36	$51.35	$51.40
Purchase #3	$72.78	8.287%	$78.8113	$78.81	$78.80	$78.80
Purchase #4	$108.25	7.756%	$116.6459	$116.65	$116.65	$116.60
Purchase #5	$137.40	4.452%	$143.517	$143.52	$143.50	$143.50
Purchase #6	$138.27	5.267%	$145.5527	$145.55	$145.55	$145.60
Purchase #7	$16.71	5.257%	$17.5884	$17.59	$17.60	$17.60
7 purchase totals =	$706.00		$751.9186	$751.92	$751.90	$751.90