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	$44.47	4.704%	$46.5619	$46.56	$46.55	$46.60
Purchase #2	$13.51	4.265%	$14.0862	$14.09	$14.10	$14.10
Purchase #3	$28.56	3.874%	$29.6664	$29.67	$29.65	$29.70
Purchase #4	$73.48	7.202%	$78.772	$78.77	$78.75	$78.80
Purchase #5	$122.33	12.129%	$137.1674	$137.17	$137.15	$137.20
Purchase #6	$76.42	12.410%	$85.9037	$85.90	$85.90	$85.90
Purchase #7	$97.45	3.255%	$100.622	$100.62	$100.60	$100.60
7 purchase totals =	$456.22		$492.7796	$492.78	$492.70	$492.90