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	$137.83	11.828%	$154.1325	$154.13	$154.15	$154.10
Purchase #2	$216.32	6.850%	$231.1379	$231.14	$231.15	$231.10
Purchase #3	$104.51	7.658%	$112.5134	$112.51	$112.50	$112.50
Purchase #4	$47.60	10.210%	$52.46	$52.46	$52.45	$52.50
Purchase #5	$77.46	5.794%	$81.948	$81.95	$81.95	$81.90
Purchase #6	$10.78	6.118%	$11.4395	$11.44	$11.45	$11.40
Purchase #7	$138.74	3.284%	$143.2962	$143.30	$143.30	$143.30
7 purchase totals =	$733.24		$786.9275	$786.93	$786.95	$786.80