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	$145.61	4.741%	$152.5134	$152.51	$152.50	$152.50
Purchase #2	$104.85	6.321%	$111.4776	$111.48	$111.50	$111.50
Purchase #3	$143.58	8.579%	$155.8977	$155.90	$155.90	$155.90
Purchase #4	$151.38	8.615%	$164.4214	$164.42	$164.40	$164.40
Purchase #5	$242.89	4.106%	$252.8631	$252.86	$252.85	$252.90
Purchase #6	$103.56	12.328%	$116.3269	$116.33	$116.35	$116.30
Purchase #7	$210.62	7.557%	$226.5366	$226.54	$226.55	$226.50
7 purchase totals =	$1,102.49		$1,180.0367	$1,180.04	$1,180.05	$1,180.00