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	$113.52	4.392%	$118.5058	$118.51	$118.50	$118.50
Purchase #2	$130.54	9.226%	$142.5836	$142.58	$142.60	$142.60
Purchase #3	$17.72	9.651%	$19.4302	$19.43	$19.45	$19.40
Purchase #4	$138.57	4.579%	$144.9151	$144.92	$144.90	$144.90
Purchase #5	$173.85	9.638%	$190.6057	$190.61	$190.60	$190.60
Purchase #6	$50.92	3.846%	$52.8784	$52.88	$52.90	$52.90
Purchase #7	$95.44	7.380%	$102.4835	$102.48	$102.50	$102.50
7 purchase totals =	$720.56		$771.4023	$771.41	$771.45	$771.40