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	$132.64	3.168%	$136.842	$136.84	$136.85	$136.80
Purchase #2	$83.89	8.207%	$90.7749	$90.77	$90.75	$90.80
Purchase #3	$96.38	4.661%	$100.8723	$100.87	$100.85	$100.90
Purchase #4	$153.35	6.377%	$163.1291	$163.13	$163.15	$163.10
Purchase #5	$246.36	3.727%	$255.5418	$255.54	$255.55	$255.50
Purchase #6	$101.62	10.710%	$112.5035	$112.50	$112.50	$112.50
Purchase #7	$48.47	12.316%	$54.4396	$54.44	$54.45	$54.40
7 purchase totals =	$862.71		$914.1032	$914.09	$914.10	$914.00