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	$55.91	10.664%	$61.8722	$61.87	$61.85	$61.90
Purchase #2	$37.78	12.510%	$42.5063	$42.51	$42.50	$42.50
Purchase #3	$15.83	9.203%	$17.2868	$17.29	$17.30	$17.30
Purchase #4	$153.42	7.385%	$164.7501	$164.75	$164.75	$164.80
Purchase #5	$61.62	8.617%	$66.9298	$66.93	$66.95	$66.90
Purchase #6	$223.27	8.136%	$241.4352	$241.44	$241.45	$241.40
Purchase #7	$134.88	3.593%	$139.7262	$139.73	$139.75	$139.70
7 purchase totals =	$682.71		$734.5066	$734.52	$734.55	$734.50