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	$157.46	11.119%	$174.968	$174.97	$174.95	$175.00
Purchase #2	$168.28	3.204%	$173.6717	$173.67	$173.65	$173.70
Purchase #3	$217.88	9.382%	$238.3215	$238.32	$238.30	$238.30
Purchase #4	$39.70	7.225%	$42.5683	$42.57	$42.55	$42.60
Purchase #5	$95.37	8.307%	$103.2924	$103.29	$103.30	$103.30
Purchase #6	$157.81	4.332%	$164.6463	$164.65	$164.65	$164.60
Purchase #7	$89.86	11.407%	$100.1103	$100.11	$100.10	$100.10
7 purchase totals =	$926.36		$997.5785	$997.58	$997.50	$997.60