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	$160.25	13.736%	$182.2619	$182.26	$182.25	$182.30
Purchase #2	$132.67	13.774%	$150.944	$150.94	$150.95	$150.90
Purchase #3	$75.52	4.145%	$78.6503	$78.65	$78.65	$78.70
Purchase #4	$157.36	13.724%	$178.9561	$178.96	$178.95	$179.00
Purchase #5	$104.86	6.565%	$111.7441	$111.74	$111.75	$111.70
Purchase #6	$55.50	13.538%	$63.0136	$63.01	$63.00	$63.00
Purchase #7	$238.90	9.231%	$260.9529	$260.95	$260.95	$261.00
7 purchase totals =	$925.06		$1,026.5229	$1,026.51	$1,026.50	$1,026.60