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	$231.88	11.754%	$259.1352	$259.14	$259.15	$259.10
Purchase #2	$111.55	4.426%	$116.4872	$116.49	$116.50	$116.50
Purchase #3	$147.71	4.245%	$153.9803	$153.98	$154.00	$154.00
Purchase #4	$130.42	5.313%	$137.3492	$137.35	$137.35	$137.30
Purchase #5	$185.30	11.651%	$206.8893	$206.89	$206.90	$206.90
Purchase #6	$244.31	7.460%	$262.5355	$262.54	$262.55	$262.50
Purchase #7	$67.46	7.635%	$72.6106	$72.61	$72.60	$72.60
7 purchase totals =	$1,118.63		$1,208.9873	$1,209.00	$1,209.05	$1,208.90