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	$205.55	5.785%	$217.4411	$217.44	$217.45	$217.40
Purchase #2	$23.99	12.631%	$27.0202	$27.02	$27.00	$27.00
Purchase #3	$185.44	6.189%	$196.9169	$196.92	$196.90	$196.90
Purchase #4	$174.97	6.144%	$185.7202	$185.72	$185.70	$185.70
Purchase #5	$249.63	8.693%	$271.3303	$271.33	$271.35	$271.30
Purchase #6	$100.76	12.318%	$113.1716	$113.17	$113.15	$113.20
Purchase #7	$29.59	9.467%	$32.3913	$32.39	$32.40	$32.40
7 purchase totals =	$969.93		$1,043.9916	$1,043.99	$1,043.95	$1,043.90