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	$39.38	11.725%	$43.9973	$44.00	$44.00	$44.00
Purchase #2	$43.68	8.212%	$47.267	$47.27	$47.25	$47.30
Purchase #3	$249.81	9.636%	$273.8817	$273.88	$273.90	$273.90
Purchase #4	$30.43	3.140%	$31.3855	$31.39	$31.40	$31.40
Purchase #5	$50.78	4.382%	$53.0052	$53.01	$53.00	$53.00
Purchase #6	$93.29	8.132%	$100.8763	$100.88	$100.90	$100.90
Purchase #7	$125.94	9.874%	$138.3753	$138.38	$138.40	$138.40
7 purchase totals =	$633.31		$688.7883	$688.81	$688.85	$688.90