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	$141.27	9.439%	$154.6045	$154.60	$154.60	$154.60
Purchase #2	$246.51	3.357%	$254.7853	$254.79	$254.80	$254.80
Purchase #3	$224.98	10.393%	$248.3622	$248.36	$248.35	$248.40
Purchase #4	$57.52	10.441%	$63.5257	$63.53	$63.55	$63.50
Purchase #5	$228.97	10.837%	$253.7835	$253.78	$253.80	$253.80
Purchase #6	$100.86	8.578%	$109.5118	$109.51	$109.50	$109.50
Purchase #7	$211.27	5.377%	$222.63	$222.63	$222.65	$222.60
7 purchase totals =	$1,211.38		$1,307.2030	$1,307.20	$1,307.25	$1,307.20