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	$190.32	9.461%	$208.3262	$208.33	$208.35	$208.30
Purchase #2	$126.97	6.205%	$134.8485	$134.85	$134.85	$134.80
Purchase #3	$174.97	12.268%	$196.4353	$196.44	$196.45	$196.40
Purchase #4	$175.55	11.838%	$196.3316	$196.33	$196.35	$196.30
Purchase #5	$66.90	9.686%	$73.3799	$73.38	$73.40	$73.40
Purchase #6	$144.95	4.510%	$151.4872	$151.49	$151.50	$151.50
Purchase #7	$197.36	11.308%	$219.6775	$219.68	$219.70	$219.70
7 purchase totals =	$1,077.02		$1,180.4862	$1,180.50	$1,180.60	$1,180.40