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	$217.64	5.306%	$229.188	$229.19	$229.20	$229.20
Purchase #2	$36.59	11.676%	$40.8622	$40.86	$40.85	$40.90
Purchase #3	$38.74	7.233%	$41.5421	$41.54	$41.55	$41.50
Purchase #4	$238.26	10.324%	$262.858	$262.86	$262.85	$262.90
Purchase #5	$246.72	13.868%	$280.9351	$280.94	$280.95	$280.90
Purchase #6	$233.78	10.388%	$258.0651	$258.07	$258.05	$258.10
Purchase #7	$39.60	11.212%	$44.04	$44.04	$44.05	$44.00
7 purchase totals =	$1,051.33		$1,157.4905	$1,157.50	$1,157.50	$1,157.50