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	$220.51	10.541%	$243.754	$243.75	$243.75	$243.80
Purchase #2	$63.47	13.720%	$72.1781	$72.18	$72.20	$72.20
Purchase #3	$143.87	5.847%	$152.2821	$152.28	$152.30	$152.30
Purchase #4	$107.67	8.230%	$116.5312	$116.53	$116.55	$116.50
Purchase #5	$13.91	5.706%	$14.7037	$14.70	$14.70	$14.70
Purchase #6	$97.32	3.724%	$100.9442	$100.94	$100.95	$100.90
Purchase #7	$53.33	12.156%	$59.8128	$59.81	$59.80	$59.80
7 purchase totals =	$700.08		$760.2061	$760.19	$760.25	$760.20