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	$171.77	4.551%	$179.5873	$179.59	$179.60	$179.60
Purchase #2	$43.59	6.785%	$46.5476	$46.55	$46.55	$46.50
Purchase #3	$47.45	5.397%	$50.0109	$50.01	$50.00	$50.00
Purchase #4	$40.74	12.663%	$45.8989	$45.90	$45.90	$45.90
Purchase #5	$143.72	6.640%	$153.263	$153.26	$153.25	$153.30
Purchase #6	$176.38	3.158%	$181.9501	$181.95	$181.95	$182.00
Purchase #7	$243.64	11.577%	$271.8462	$271.85	$271.85	$271.80
7 purchase totals =	$867.29		$929.1040	$929.11	$929.10	$929.10