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	$78.53	8.585%	$85.2718	$85.27	$85.25	$85.30
Purchase #2	$113.77	12.386%	$127.8616	$127.86	$127.85	$127.90
Purchase #3	$158.52	8.750%	$172.3905	$172.39	$172.40	$172.40
Purchase #4	$12.36	9.490%	$13.533	$13.53	$13.55	$13.50
Purchase #5	$78.31	3.767%	$81.2599	$81.26	$81.25	$81.30
Purchase #6	$61.86	11.591%	$69.0302	$69.03	$69.05	$69.00
Purchase #7	$75.34	4.207%	$78.5096	$78.51	$78.50	$78.50
7 purchase totals =	$578.69		$627.8566	$627.85	$627.85	$627.90