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	$131.96	7.595%	$141.9824	$141.98	$142.00	$142.00
Purchase #2	$221.94	8.379%	$240.5364	$240.54	$240.55	$240.50
Purchase #3	$36.87	5.390%	$38.8573	$38.86	$38.85	$38.90
Purchase #4	$70.80	5.245%	$74.5135	$74.51	$74.50	$74.50
Purchase #5	$240.50	3.353%	$248.564	$248.56	$248.55	$248.60
Purchase #6	$132.90	3.623%	$137.715	$137.72	$137.70	$137.70
Purchase #7	$93.60	7.484%	$100.605	$100.61	$100.60	$100.60
7 purchase totals =	$928.57		$982.7736	$982.78	$982.75	$982.80