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	$219.29	10.260%	$241.7892	$241.79	$241.80	$241.80
Purchase #2	$84.36	5.553%	$89.0445	$89.04	$89.05	$89.00
Purchase #3	$174.63	4.291%	$182.1234	$182.12	$182.10	$182.10
Purchase #4	$76.92	5.801%	$81.3821	$81.38	$81.40	$81.40
Purchase #5	$31.97	12.147%	$35.8534	$35.85	$35.85	$35.90
Purchase #6	$41.42	10.527%	$45.7803	$45.78	$45.80	$45.80
Purchase #7	$148.94	4.463%	$155.5872	$155.59	$155.60	$155.60
7 purchase totals =	$777.53		$831.5601	$831.55	$831.60	$831.60