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	$38.35	12.781%	$43.2515	$43.25	$43.25	$43.30
Purchase #2	$85.49	11.188%	$95.0546	$95.05	$95.05	$95.10
Purchase #3	$112.71	4.761%	$118.0761	$118.08	$118.10	$118.10
Purchase #4	$37.66	3.339%	$38.9175	$38.92	$38.90	$38.90
Purchase #5	$109.52	3.841%	$113.7267	$113.73	$113.75	$113.70
Purchase #6	$96.50	10.815%	$106.9365	$106.94	$106.95	$106.90
Purchase #7	$48.85	3.338%	$50.4806	$50.48	$50.50	$50.50
7 purchase totals =	$529.08		$566.4435	$566.45	$566.50	$566.50