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	$69.44	4.725%	$72.721	$72.72	$72.70	$72.70
Purchase #2	$21.90	11.285%	$24.3714	$24.37	$24.35	$24.40
Purchase #3	$171.68	7.782%	$185.0401	$185.04	$185.05	$185.00
Purchase #4	$54.55	13.752%	$62.0517	$62.05	$62.05	$62.10
Purchase #5	$151.48	11.187%	$168.4261	$168.43	$168.45	$168.40
Purchase #6	$208.89	10.138%	$230.0673	$230.07	$230.05	$230.10
Purchase #7	$33.64	8.768%	$36.5896	$36.59	$36.60	$36.60
7 purchase totals =	$711.58		$779.2672	$779.27	$779.25	$779.30