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	$81.32	10.504%	$89.8619	$89.86	$89.85	$89.90
Purchase #2	$123.68	6.266%	$131.4298	$131.43	$131.45	$131.40
Purchase #3	$21.72	5.553%	$22.9261	$22.93	$22.95	$22.90
Purchase #4	$54.46	11.167%	$60.5415	$60.54	$60.55	$60.50
Purchase #5	$217.25	6.297%	$230.9302	$230.93	$230.95	$230.90
Purchase #6	$214.26	8.257%	$231.9514	$231.95	$231.95	$232.00
Purchase #7	$32.87	9.195%	$35.8924	$35.89	$35.90	$35.90
7 purchase totals =	$745.56		$803.5333	$803.53	$803.60	$803.50