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	$114.93	5.353%	$121.0822	$121.08	$121.10	$121.10
Purchase #2	$158.44	12.268%	$177.8774	$177.88	$177.90	$177.90
Purchase #3	$213.56	6.130%	$226.6512	$226.65	$226.65	$226.70
Purchase #4	$119.34	10.509%	$131.8814	$131.88	$131.90	$131.90
Purchase #5	$162.52	10.423%	$179.4595	$179.46	$179.45	$179.50
Purchase #6	$179.95	9.380%	$196.8293	$196.83	$196.85	$196.80
Purchase #7	$198.87	4.610%	$208.0379	$208.04	$208.05	$208.00
7 purchase totals =	$1,147.61		$1,241.8189	$1,241.82	$1,241.90	$1,241.90