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	$80.53	8.316%	$87.2269	$87.23	$87.25	$87.20
Purchase #2	$208.58	11.838%	$233.2717	$233.27	$233.25	$233.30
Purchase #3	$62.65	4.138%	$65.2425	$65.24	$65.25	$65.20
Purchase #4	$39.42	8.416%	$42.7376	$42.74	$42.75	$42.70
Purchase #5	$86.83	5.303%	$91.4346	$91.43	$91.45	$91.40
Purchase #6	$34.82	10.785%	$38.5753	$38.58	$38.60	$38.60
Purchase #7	$166.71	11.248%	$185.4615	$185.46	$185.45	$185.50
7 purchase totals =	$679.54		$743.9501	$743.95	$744.00	$743.90