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	$191.78	8.856%	$208.764	$208.76	$208.75	$208.80
Purchase #2	$233.56	5.658%	$246.7748	$246.77	$246.75	$246.80
Purchase #3	$210.39	5.799%	$222.5905	$222.59	$222.60	$222.60
Purchase #4	$156.61	12.671%	$176.4541	$176.45	$176.45	$176.50
Purchase #5	$188.80	8.589%	$205.016	$205.02	$205.00	$205.00
Purchase #6	$49.33	10.590%	$54.554	$54.55	$54.55	$54.60
Purchase #7	$112.94	9.578%	$123.7574	$123.76	$123.75	$123.80
7 purchase totals =	$1,143.41		$1,237.9108	$1,237.90	$1,237.85	$1,238.10