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	$147.34	4.131%	$153.4266	$153.43	$153.45	$153.40
Purchase #2	$177.82	12.860%	$200.6877	$200.69	$200.70	$200.70
Purchase #3	$233.64	12.552%	$262.9665	$262.97	$262.95	$263.00
Purchase #4	$70.90	13.161%	$80.2311	$80.23	$80.25	$80.20
Purchase #5	$35.83	13.638%	$40.7165	$40.72	$40.70	$40.70
Purchase #6	$206.40	7.798%	$222.4951	$222.50	$222.50	$222.50
Purchase #7	$138.76	13.186%	$157.0569	$157.06	$157.05	$157.10
7 purchase totals =	$1,010.69		$1,117.5804	$1,117.60	$1,117.60	$1,117.60