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	$13.45	8.526%	$14.5967	$14.60	$14.60	$14.60
Purchase #2	$120.90	6.624%	$128.9084	$128.91	$128.90	$128.90
Purchase #3	$112.95	5.762%	$119.4582	$119.46	$119.45	$119.50
Purchase #4	$84.76	4.204%	$88.3233	$88.32	$88.30	$88.30
Purchase #5	$105.83	12.314%	$118.8619	$118.86	$118.85	$118.90
Purchase #6	$44.66	4.354%	$46.6045	$46.60	$46.60	$46.60
Purchase #7	$19.56	3.379%	$20.2209	$20.22	$20.20	$20.20
7 purchase totals =	$502.11		$536.9739	$536.97	$536.90	$537.00