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	$67.94	10.186%	$74.8604	$74.86	$74.85	$74.90
Purchase #2	$164.61	12.792%	$185.6669	$185.67	$185.65	$185.70
Purchase #3	$222.56	3.749%	$230.9038	$230.90	$230.90	$230.90
Purchase #4	$162.64	8.509%	$176.479	$176.48	$176.50	$176.50
Purchase #5	$105.93	11.747%	$118.3736	$118.37	$118.35	$118.40
Purchase #6	$101.81	9.642%	$111.6265	$111.63	$111.65	$111.60
Purchase #7	$177.70	12.788%	$200.4243	$200.42	$200.40	$200.40
7 purchase totals =	$1,003.19		$1,098.3345	$1,098.33	$1,098.30	$1,098.40