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	$145.86	12.437%	$164.0006	$164.00	$164.00	$164.00
Purchase #2	$156.97	10.746%	$173.838	$173.84	$173.85	$173.80
Purchase #3	$9.93	8.133%	$10.7376	$10.74	$10.75	$10.70
Purchase #4	$16.57	7.774%	$17.8582	$17.86	$17.85	$17.90
Purchase #5	$76.37	7.724%	$82.2688	$82.27	$82.25	$82.30
Purchase #6	$160.94	3.332%	$166.3025	$166.30	$166.30	$166.30
Purchase #7	$90.85	10.692%	$100.5637	$100.56	$100.55	$100.60
7 purchase totals =	$657.49		$715.5694	$715.57	$715.55	$715.60