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	$106.36	5.166%	$111.8546	$111.85	$111.85	$111.90
Purchase #2	$183.64	12.854%	$207.2451	$207.25	$207.25	$207.20
Purchase #3	$40.27	7.788%	$43.4062	$43.41	$43.40	$43.40
Purchase #4	$41.40	11.568%	$46.1892	$46.19	$46.20	$46.20
Purchase #5	$49.70	11.540%	$55.4354	$55.44	$55.45	$55.40
Purchase #6	$37.60	10.116%	$41.4036	$41.40	$41.40	$41.40
Purchase #7	$234.30	12.605%	$263.8335	$263.83	$263.85	$263.80
7 purchase totals =	$693.27		$769.3676	$769.37	$769.40	$769.30