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	$14.59	10.130%	$16.068	$16.07	$16.05	$16.10
Purchase #2	$182.29	10.746%	$201.8789	$201.88	$201.90	$201.90
Purchase #3	$174.68	12.612%	$196.7106	$196.71	$196.70	$196.70
Purchase #4	$106.73	4.488%	$111.52	$111.52	$111.50	$111.50
Purchase #5	$51.43	12.488%	$57.8526	$57.85	$57.85	$57.90
Purchase #6	$69.36	13.277%	$78.5689	$78.57	$78.55	$78.60
Purchase #7	$116.67	8.756%	$126.8856	$126.89	$126.90	$126.90
7 purchase totals =	$715.75		$789.4846	$789.49	$789.45	$789.60