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	$68.50	4.482%	$71.5702	$71.57	$71.55	$71.60
Purchase #2	$237.87	11.814%	$265.972	$265.97	$265.95	$266.00
Purchase #3	$242.72	9.426%	$265.5988	$265.60	$265.60	$265.60
Purchase #4	$19.32	11.547%	$21.5509	$21.55	$21.55	$21.60
Purchase #5	$140.27	12.543%	$157.8641	$157.86	$157.85	$157.90
Purchase #6	$131.47	8.379%	$142.4859	$142.49	$142.50	$142.50
Purchase #7	$235.61	3.275%	$243.3262	$243.33	$243.35	$243.30
7 purchase totals =	$1,075.76		$1,168.3681	$1,168.37	$1,168.35	$1,168.50