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	$32.39	9.666%	$35.5208	$35.52	$35.50	$35.50
Purchase #2	$164.27	12.455%	$184.7298	$184.73	$184.75	$184.70
Purchase #3	$74.69	4.853%	$78.3147	$78.31	$78.30	$78.30
Purchase #4	$235.50	11.409%	$262.3682	$262.37	$262.35	$262.40
Purchase #5	$173.27	9.313%	$189.4066	$189.41	$189.40	$189.40
Purchase #6	$218.52	5.430%	$230.3856	$230.39	$230.40	$230.40
Purchase #7	$209.40	12.521%	$235.619	$235.62	$235.60	$235.60
7 purchase totals =	$1,108.04		$1,216.3447	$1,216.35	$1,216.30	$1,216.30