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	$93.37	10.471%	$103.1468	$103.15	$103.15	$103.10
Purchase #2	$39.93	9.151%	$43.584	$43.58	$43.60	$43.60
Purchase #3	$217.38	6.642%	$231.8184	$231.82	$231.80	$231.80
Purchase #4	$28.34	9.842%	$31.1292	$31.13	$31.15	$31.10
Purchase #5	$12.59	13.755%	$14.3218	$14.32	$14.30	$14.30
Purchase #6	$69.75	5.808%	$73.8011	$73.80	$73.80	$73.80
Purchase #7	$192.52	9.128%	$210.0932	$210.09	$210.10	$210.10
7 purchase totals =	$653.88		$707.8945	$707.89	$707.90	$707.80