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	$237.30	10.828%	$262.9948	$262.99	$263.00	$263.00
Purchase #2	$107.90	9.191%	$117.8171	$117.82	$117.80	$117.80
Purchase #3	$151.93	8.395%	$164.6845	$164.68	$164.70	$164.70
Purchase #4	$70.57	11.853%	$78.9347	$78.93	$78.95	$78.90
Purchase #5	$40.62	8.192%	$43.9476	$43.95	$43.95	$43.90
Purchase #6	$16.96	5.635%	$17.9157	$17.92	$17.90	$17.90
Purchase #7	$67.61	7.443%	$72.6422	$72.64	$72.65	$72.60
7 purchase totals =	$692.89		$758.9366	$758.93	$758.95	$758.80