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	$186.60	13.584%	$211.9477	$211.95	$211.95	$211.90
Purchase #2	$166.55	11.862%	$186.3062	$186.31	$186.30	$186.30
Purchase #3	$173.37	13.345%	$196.5062	$196.51	$196.50	$196.50
Purchase #4	$205.38	5.464%	$216.602	$216.60	$216.60	$216.60
Purchase #5	$153.31	3.175%	$158.1776	$158.18	$158.20	$158.20
Purchase #6	$180.44	5.232%	$189.8806	$189.88	$189.90	$189.90
Purchase #7	$167.42	13.699%	$190.3549	$190.35	$190.35	$190.40
7 purchase totals =	$1,233.07		$1,349.7752	$1,349.78	$1,349.80	$1,349.80