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	$218.95	9.818%	$240.4465	$240.45	$240.45	$240.40
Purchase #2	$96.50	8.477%	$104.6803	$104.68	$104.70	$104.70
Purchase #3	$107.53	9.400%	$117.6378	$117.64	$117.65	$117.60
Purchase #4	$69.81	3.690%	$72.386	$72.39	$72.40	$72.40
Purchase #5	$102.30	3.105%	$105.4764	$105.48	$105.50	$105.50
Purchase #6	$183.93	4.671%	$192.5214	$192.52	$192.50	$192.50
Purchase #7	$205.38	12.836%	$231.7426	$231.74	$231.75	$231.70
7 purchase totals =	$984.40		$1,064.8910	$1,064.90	$1,064.95	$1,064.80