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	$51.98	10.859%	$57.6245	$57.62	$57.60	$57.60
Purchase #2	$163.97	8.156%	$177.3434	$177.34	$177.35	$177.30
Purchase #3	$196.41	13.429%	$222.7859	$222.79	$222.80	$222.80
Purchase #4	$61.32	5.779%	$64.8637	$64.86	$64.85	$64.90
Purchase #5	$203.34	3.542%	$210.5423	$210.54	$210.55	$210.50
Purchase #6	$214.43	7.711%	$230.9647	$230.96	$230.95	$231.00
Purchase #7	$52.98	3.657%	$54.9175	$54.92	$54.90	$54.90
7 purchase totals =	$944.43		$1,019.0420	$1,019.03	$1,019.00	$1,019.00