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	$176.27	13.667%	$200.3608	$200.36	$200.35	$200.40
Purchase #2	$90.93	9.843%	$99.8802	$99.88	$99.90	$99.90
Purchase #3	$14.73	5.204%	$15.4965	$15.50	$15.50	$15.50
Purchase #4	$49.37	12.380%	$55.482	$55.48	$55.50	$55.50
Purchase #5	$68.43	5.653%	$72.2983	$72.30	$72.30	$72.30
Purchase #6	$250.37	4.542%	$261.7418	$261.74	$261.75	$261.70
Purchase #7	$241.83	7.105%	$259.012	$259.01	$259.00	$259.00
7 purchase totals =	$891.93		$964.2716	$964.27	$964.30	$964.30