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	$120.61	8.625%	$131.0126	$131.01	$131.00	$131.00
Purchase #2	$105.78	8.164%	$114.4159	$114.42	$114.40	$114.40
Purchase #3	$83.50	4.782%	$87.493	$87.49	$87.50	$87.50
Purchase #4	$239.39	3.438%	$247.6202	$247.62	$247.60	$247.60
Purchase #5	$28.30	13.866%	$32.2241	$32.22	$32.20	$32.20
Purchase #6	$200.42	11.433%	$223.334	$223.33	$223.35	$223.30
Purchase #7	$181.52	8.516%	$196.9782	$196.98	$197.00	$197.00
7 purchase totals =	$959.52		$1,033.0780	$1,033.07	$1,033.05	$1,033.00