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	$185.89	5.680%	$196.4486	$196.45	$196.45	$196.40
Purchase #2	$8.85	11.249%	$9.8455	$9.85	$9.85	$9.80
Purchase #3	$100.45	5.161%	$105.6342	$105.63	$105.65	$105.60
Purchase #4	$103.70	3.135%	$106.951	$106.95	$106.95	$107.00
Purchase #5	$24.75	12.736%	$27.9022	$27.90	$27.90	$27.90
Purchase #6	$19.67	8.367%	$21.3158	$21.32	$21.30	$21.30
Purchase #7	$137.38	7.685%	$147.9377	$147.94	$147.95	$147.90
7 purchase totals =	$580.69		$616.0350	$616.04	$616.05	$615.90