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	$181.77	8.345%	$196.9387	$196.94	$196.95	$196.90
Purchase #2	$183.50	13.601%	$208.4578	$208.46	$208.45	$208.50
Purchase #3	$236.29	10.838%	$261.8991	$261.90	$261.90	$261.90
Purchase #4	$40.86	12.768%	$46.077	$46.08	$46.10	$46.10
Purchase #5	$18.37	7.481%	$19.7443	$19.74	$19.75	$19.70
Purchase #6	$141.93	3.783%	$147.2992	$147.30	$147.30	$147.30
Purchase #7	$117.83	5.583%	$124.4084	$124.41	$124.40	$124.40
7 purchase totals =	$920.55		$1,004.8245	$1,004.83	$1,004.85	$1,004.80