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	$187.45	4.641%	$196.1496	$196.15	$196.15	$196.10
Purchase #2	$117.48	4.387%	$122.6338	$122.63	$122.65	$122.60
Purchase #3	$126.85	9.747%	$139.2141	$139.21	$139.20	$139.20
Purchase #4	$137.93	5.590%	$145.6403	$145.64	$145.65	$145.60
Purchase #5	$132.67	5.251%	$139.6365	$139.64	$139.65	$139.60
Purchase #6	$103.59	3.639%	$107.3596	$107.36	$107.35	$107.40
Purchase #7	$100.59	3.266%	$103.8753	$103.88	$103.90	$103.90
7 purchase totals =	$906.56		$954.5092	$954.51	$954.55	$954.40