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	$88.53	11.102%	$98.3586	$98.36	$98.35	$98.40
Purchase #2	$47.27	8.198%	$51.1452	$51.15	$51.15	$51.10
Purchase #3	$106.42	4.799%	$111.5271	$111.53	$111.55	$111.50
Purchase #4	$174.53	12.496%	$196.3393	$196.34	$196.35	$196.30
Purchase #5	$48.87	9.531%	$53.5278	$53.53	$53.55	$53.50
Purchase #6	$78.84	3.863%	$81.8856	$81.89	$81.90	$81.90
Purchase #7	$155.54	11.699%	$173.7366	$173.74	$173.75	$173.70
7 purchase totals =	$700.00		$766.5202	$766.54	$766.60	$766.40