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	$207.62	6.527%	$221.1714	$221.17	$221.15	$221.20
Purchase #2	$79.85	10.215%	$88.0067	$88.01	$88.00	$88.00
Purchase #3	$182.75	9.186%	$199.5374	$199.54	$199.55	$199.50
Purchase #4	$182.55	8.151%	$197.4297	$197.43	$197.45	$197.40
Purchase #5	$163.25	6.512%	$173.8808	$173.88	$173.90	$173.90
Purchase #6	$87.76	3.615%	$90.9325	$90.93	$90.95	$90.90
Purchase #7	$42.97	6.604%	$45.8077	$45.81	$45.80	$45.80
7 purchase totals =	$946.75		$1,016.7662	$1,016.77	$1,016.80	$1,016.70