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	$79.68	4.362%	$83.1556	$83.16	$83.15	$83.20
Purchase #2	$19.47	12.868%	$21.9754	$21.98	$22.00	$22.00
Purchase #3	$57.78	3.111%	$59.5775	$59.58	$59.60	$59.60
Purchase #4	$140.86	9.509%	$154.2544	$154.25	$154.25	$154.30
Purchase #5	$168.88	7.138%	$180.9347	$180.93	$180.95	$180.90
Purchase #6	$150.75	13.771%	$171.5098	$171.51	$171.50	$171.50
Purchase #7	$58.42	11.508%	$65.143	$65.14	$65.15	$65.10
7 purchase totals =	$675.84		$736.5504	$736.55	$736.60	$736.60