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	$118.83	5.778%	$125.696	$125.70	$125.70	$125.70
Purchase #2	$188.56	11.572%	$210.3802	$210.38	$210.40	$210.40
Purchase #3	$171.86	9.288%	$187.8224	$187.82	$187.80	$187.80
Purchase #4	$125.41	5.269%	$132.0179	$132.02	$132.00	$132.00
Purchase #5	$147.95	7.667%	$159.2933	$159.29	$159.30	$159.30
Purchase #6	$182.47	5.554%	$192.6044	$192.60	$192.60	$192.60
Purchase #7	$81.68	10.766%	$90.4737	$90.47	$90.45	$90.50
7 purchase totals =	$1,016.76		$1,098.2879	$1,098.28	$1,098.25	$1,098.30