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	$102.25	11.820%	$114.336	$114.34	$114.35	$114.30
Purchase #2	$40.35	12.463%	$45.3788	$45.38	$45.40	$45.40
Purchase #3	$200.39	13.522%	$227.4867	$227.49	$227.50	$227.50
Purchase #4	$90.65	13.358%	$102.759	$102.76	$102.75	$102.80
Purchase #5	$76.27	13.121%	$86.2774	$86.28	$86.30	$86.30
Purchase #6	$34.91	3.403%	$36.098	$36.10	$36.10	$36.10
Purchase #7	$197.47	5.368%	$208.0702	$208.07	$208.05	$208.10
7 purchase totals =	$742.29		$820.4061	$820.42	$820.45	$820.50