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	$143.95	11.156%	$160.0091	$160.01	$160.00	$160.00
Purchase #2	$168.42	11.364%	$187.5592	$187.56	$187.55	$187.60
Purchase #3	$70.35	8.380%	$76.2453	$76.25	$76.25	$76.20
Purchase #4	$80.80	12.325%	$90.7586	$90.76	$90.75	$90.80
Purchase #5	$218.81	5.843%	$231.5951	$231.60	$231.60	$231.60
Purchase #6	$225.27	7.276%	$241.6606	$241.66	$241.65	$241.70
Purchase #7	$128.48	11.682%	$143.489	$143.49	$143.50	$143.50
7 purchase totals =	$1,036.08		$1,131.3169	$1,131.33	$1,131.30	$1,131.40