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	$40.88	6.487%	$43.5319	$43.53	$43.55	$43.50
Purchase #2	$147.59	3.675%	$153.0139	$153.01	$153.00	$153.00
Purchase #3	$231.48	10.596%	$256.0076	$256.01	$256.00	$256.00
Purchase #4	$50.39	13.443%	$57.1639	$57.16	$57.15	$57.20
Purchase #5	$249.28	12.366%	$280.106	$280.11	$280.10	$280.10
Purchase #6	$198.90	5.706%	$210.2492	$210.25	$210.25	$210.20
Purchase #7	$138.98	13.783%	$158.1356	$158.14	$158.15	$158.10
7 purchase totals =	$1,057.50		$1,158.2081	$1,158.21	$1,158.20	$1,158.10