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	$182.39	6.292%	$193.866	$193.87	$193.85	$193.90
Purchase #2	$98.69	3.699%	$102.3405	$102.34	$102.35	$102.30
Purchase #3	$75.32	10.312%	$83.087	$83.09	$83.10	$83.10
Purchase #4	$196.50	5.106%	$206.5333	$206.53	$206.55	$206.50
Purchase #5	$29.42	9.512%	$32.2184	$32.22	$32.20	$32.20
Purchase #6	$102.73	11.208%	$114.244	$114.24	$114.25	$114.20
Purchase #7	$80.85	11.798%	$90.3887	$90.39	$90.40	$90.40
7 purchase totals =	$765.90		$822.6779	$822.68	$822.70	$822.60