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	$210.88	9.284%	$230.4581	$230.46	$230.45	$230.50
Purchase #2	$181.52	3.438%	$187.7607	$187.76	$187.75	$187.80
Purchase #3	$162.38	13.660%	$184.5611	$184.56	$184.55	$184.60
Purchase #4	$62.39	5.812%	$66.0161	$66.02	$66.00	$66.00
Purchase #5	$36.49	13.725%	$41.4983	$41.50	$41.50	$41.50
Purchase #6	$149.48	8.747%	$162.555	$162.56	$162.55	$162.60
Purchase #7	$132.80	7.299%	$142.4931	$142.49	$142.50	$142.50
7 purchase totals =	$935.94		$1,015.3424	$1,015.35	$1,015.30	$1,015.50