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	$204.83	4.787%	$214.6352	$214.64	$214.65	$214.60
Purchase #2	$34.69	8.715%	$37.7132	$37.71	$37.70	$37.70
Purchase #3	$11.86	11.581%	$13.2335	$13.23	$13.25	$13.20
Purchase #4	$109.88	12.245%	$123.3348	$123.33	$123.35	$123.30
Purchase #5	$42.54	12.385%	$47.8086	$47.81	$47.80	$47.80
Purchase #6	$143.98	5.237%	$151.5202	$151.52	$151.50	$151.50
Purchase #7	$126.54	4.299%	$131.98	$131.98	$132.00	$132.00
7 purchase totals =	$674.32		$720.2255	$720.22	$720.25	$720.10