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	$21.79	12.423%	$24.497	$24.50	$24.50	$24.50
Purchase #2	$69.59	10.220%	$76.7021	$76.70	$76.70	$76.70
Purchase #3	$219.82	4.509%	$229.7317	$229.73	$229.75	$229.70
Purchase #4	$244.47	11.710%	$273.0974	$273.10	$273.10	$273.10
Purchase #5	$144.49	9.446%	$158.1385	$158.14	$158.15	$158.10
Purchase #6	$222.66	4.870%	$233.5035	$233.50	$233.50	$233.50
Purchase #7	$183.26	3.633%	$189.9178	$189.92	$189.90	$189.90
7 purchase totals =	$1,106.08		$1,185.5880	$1,185.59	$1,185.60	$1,185.50