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	$95.59	13.610%	$108.5998	$108.60	$108.60	$108.60
Purchase #2	$152.56	12.470%	$171.5842	$171.58	$171.60	$171.60
Purchase #3	$112.41	10.679%	$124.4143	$124.41	$124.40	$124.40
Purchase #4	$219.32	5.538%	$231.4659	$231.47	$231.45	$231.50
Purchase #5	$193.31	11.572%	$215.6798	$215.68	$215.70	$215.70
Purchase #6	$151.54	10.226%	$167.0365	$167.04	$167.05	$167.00
Purchase #7	$215.30	3.382%	$222.5814	$222.58	$222.60	$222.60
7 purchase totals =	$1,140.03		$1,241.3619	$1,241.36	$1,241.40	$1,241.40