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	$143.72	5.533%	$151.672	$151.67	$151.65	$151.70
Purchase #2	$56.52	6.130%	$59.9847	$59.98	$60.00	$60.00
Purchase #3	$169.64	4.130%	$176.6461	$176.65	$176.65	$176.60
Purchase #4	$171.62	4.105%	$178.665	$178.67	$178.65	$178.70
Purchase #5	$55.56	6.127%	$58.9642	$58.96	$58.95	$59.00
Purchase #6	$190.25	13.618%	$216.1582	$216.16	$216.15	$216.20
Purchase #7	$246.78	13.619%	$280.389	$280.39	$280.40	$280.40
7 purchase totals =	$1,034.09		$1,122.4792	$1,122.48	$1,122.45	$1,122.60