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	$170.45	6.584%	$181.6724	$181.67	$181.65	$181.70
Purchase #2	$142.52	7.295%	$152.9168	$152.92	$152.90	$152.90
Purchase #3	$76.81	11.350%	$85.5279	$85.53	$85.55	$85.50
Purchase #4	$116.45	6.724%	$124.2801	$124.28	$124.30	$124.30
Purchase #5	$187.83	12.778%	$211.8309	$211.83	$211.85	$211.80
Purchase #6	$206.80	4.798%	$216.7223	$216.72	$216.70	$216.70
Purchase #7	$186.60	3.239%	$192.644	$192.64	$192.65	$192.60
7 purchase totals =	$1,087.46		$1,165.5944	$1,165.59	$1,165.60	$1,165.50