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	$247.72	3.492%	$256.3704	$256.37	$256.35	$256.40
Purchase #2	$243.63	12.711%	$274.5978	$274.60	$274.60	$274.60
Purchase #3	$230.33	4.842%	$241.4826	$241.48	$241.50	$241.50
Purchase #4	$17.73	3.336%	$18.3215	$18.32	$18.30	$18.30
Purchase #5	$81.54	4.526%	$85.2305	$85.23	$85.25	$85.20
Purchase #6	$44.45	3.339%	$45.9342	$45.93	$45.95	$45.90
Purchase #7	$24.52	13.214%	$27.7601	$27.76	$27.75	$27.80
7 purchase totals =	$889.92		$949.6971	$949.69	$949.70	$949.70