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	$5.36	6.493%	$5.708	$5.71	$5.70	$5.70
Purchase #2	$178.76	11.519%	$199.3514	$199.35	$199.35	$199.40
Purchase #3	$91.57	4.725%	$95.8967	$95.90	$95.90	$95.90
Purchase #4	$86.77	3.229%	$89.5718	$89.57	$89.55	$89.60
Purchase #5	$37.92	5.726%	$40.0913	$40.09	$40.10	$40.10
Purchase #6	$150.56	3.856%	$156.3656	$156.37	$156.35	$156.40
Purchase #7	$138.95	13.675%	$157.9514	$157.95	$157.95	$158.00
7 purchase totals =	$689.89		$744.9362	$744.94	$744.90	$745.10