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	$250.97	7.288%	$269.2607	$269.26	$269.25	$269.30
Purchase #2	$86.54	10.265%	$95.4233	$95.42	$95.40	$95.40
Purchase #3	$224.79	6.566%	$239.5497	$239.55	$239.55	$239.50
Purchase #4	$9.62	5.738%	$10.172	$10.17	$10.15	$10.20
Purchase #5	$136.89	4.142%	$142.56	$142.56	$142.55	$142.60
Purchase #6	$143.94	4.614%	$150.5814	$150.58	$150.60	$150.60
Purchase #7	$144.61	8.238%	$156.523	$156.52	$156.50	$156.50
7 purchase totals =	$997.36		$1,064.0701	$1,064.06	$1,064.00	$1,064.10