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	$236.38	13.329%	$267.8871	$267.89	$267.90	$267.90
Purchase #2	$71.93	13.430%	$81.5902	$81.59	$81.60	$81.60
Purchase #3	$207.51	11.391%	$231.1475	$231.15	$231.15	$231.10
Purchase #4	$156.77	4.800%	$164.295	$164.30	$164.30	$164.30
Purchase #5	$66.34	9.102%	$72.3783	$72.38	$72.40	$72.40
Purchase #6	$138.53	10.843%	$153.5508	$153.55	$153.55	$153.60
Purchase #7	$17.87	4.494%	$18.6731	$18.67	$18.65	$18.70
7 purchase totals =	$895.33		$989.5220	$989.53	$989.55	$989.60