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	$13.82	11.774%	$15.4472	$15.45	$15.45	$15.40
Purchase #2	$118.96	11.608%	$132.7689	$132.77	$132.75	$132.80
Purchase #3	$62.70	7.659%	$67.5022	$67.50	$67.50	$67.50
Purchase #4	$227.87	4.818%	$238.8488	$238.85	$238.85	$238.80
Purchase #5	$45.60	8.458%	$49.4568	$49.46	$49.45	$49.50
Purchase #6	$160.92	8.835%	$175.1373	$175.14	$175.15	$175.10
Purchase #7	$48.70	11.785%	$54.4393	$54.44	$54.45	$54.40
7 purchase totals =	$678.57		$733.6005	$733.61	$733.60	$733.50